In space, with respect to an orthonormal coordinate system, we consider the points $\mathrm { A } ( 1 ; - 1 ; - 1 )$, $\mathrm { B } ( 1 ; 1 ; 1 ) , \mathrm { C } ( 0 ; 3 ; 1 )$ and the plane $\mathscr { P }$ with equation $2 x + y - z + 5 = 0$.
Let $\mathscr { D } _ { 1 }$ be the line with direction vector $\vec { u } ( 2 ; - 1 ; 1 )$ passing through A.
A parametric representation of the line $\mathscr { D } _ { 1 }$ is : a. $\left\{ \begin{array} { l } x = 2 + t \\ y = - 1 - t \\ z = 1 - t \end{array} \quad ( t \in \mathbb { R } ) \right.$ b. $\left\{ \begin{array} { l } x = - 1 + 2 t \\ y = 1 - t \\ z = 1 + t \end{array} \quad ( t \in \mathbb { R } ) \right.$ c. $\left\{ \begin{array} { l } x = 5 + 4 t \\ y = - 3 - 2 t \\ z = 1 + 2 t \end{array} \quad ( t \in \mathbb { R } ) \right.$ d. $\left\{ \begin{array} { l } x = 4 - 2 t \\ y = - 2 + t \\ z = 3 - 4 t \end{array} \quad ( t \in \mathbb { R } ) \right.$

This exercise is a multiple choice questionnaire. For each question, only one of the four proposed answers is correct. No justification is required. A wrong answer, multiple answers, or the absence of an answer to a question earns neither points nor deducts points. The four questions are independent.
Space is referred to an orthonormal coordinate system $(O; \vec{\imath}, \vec{\jmath}, \vec{k})$.

1. Consider the points $A(1; 0; 3)$ and $B(4; 1; 0)$.
   A parametric representation of the line (AB) is: a. $\left\{ \begin{aligned} x & = 3 + t \\ y & = 1 \\ z & = -3 + 3t \end{aligned} \right.$ with $t \in \mathbb{R}$ b. $\left\{ \begin{array}{l} x = 1 + 4t \\ y = 3 \\ z = 3 \end{array} \right.$ with $t \in \mathbb{R}$ c. $\left\{ \begin{aligned} x & = 1 + 3t \\ y & = t \\ z & = 3 - 3t \end{aligned} \right.$ with $t \in \mathbb{R}$ d. $\left\{ \begin{aligned} x & = 4 + t \\ y & = 1 \\ z & = 3 - 3t \end{aligned} \right.$ with $t \in \mathbb{R}$
   
2. Consider the line (d) with parametric representation $\left\{ \begin{aligned} x & = 3 + 4t \\ y & = 6t \\ z & = 4 - 2t \end{aligned} \right.$ with $t \in \mathbb{R}$
   Among the following points, which one belongs to the line (d)? a. $M(7; 6; 6)$ b. $N(3; 6; 4)$ c. $P(4; 6; -2)$ d. $R(-3; -9; 7)$
   
3. Consider the line $(d')$ with parametric representation $\left\{ \begin{aligned} x & = -2 + 3k \\ y & = -1 - 2k \\ z & = 1 + k \end{aligned} \right.$ with $k \in \mathbb{R}$
   The lines $(d)$ and $(d')$ are: a. secant b. non-coplanar c. parallel d. coincident
   
4. Consider the plane $(P)$ passing through the point $I(2; 1; 0)$ and perpendicular to the line (d).
   An equation of the plane $(P)$ is: a. $2x + 3y - z - 7 = 0$ b. $-x + y - 4z + 1 = 0$ c. $4x + 6y - 2z + 9 = 0$ d. $2x + y + 1 = 0$

Let $L _ { 1 }$ and $L _ { 2 }$ denote the lines $$\begin{aligned} & \vec { r } = \hat { i } + \lambda ( - \hat { i } + 2 \hat { j } + 2 \hat { k } ) , \lambda \in \mathbb { R } \text { and } \\ & \vec { r } = \mu ( 2 \hat { i } - \hat { j } + 2 \hat { k } ) , \mu \in \mathbb { R } \end{aligned}$$ respectively. If $L _ { 3 }$ is a line which is perpendicular to both $L _ { 1 }$ and $L _ { 2 }$ and cuts both of them, then which of the following options describe(s) $L _ { 3 }$?
(A) $\vec { r } = \frac { 2 } { 9 } ( 4 \hat { i } + \hat { j } + \hat { k } ) + t ( 2 \hat { i } + 2 \hat { j } - \hat { k } ) , t \in \mathbb { R }$
(B) $\vec { r } = \frac { 2 } { 9 } ( 2 \hat { i } - \hat { j } + 2 \hat { k } ) + t ( 2 \hat { i } + 2 \hat { j } - \hat { k } ) , t \in \mathbb { R }$
(C) $\vec { r } = \frac { 1 } { 3 } ( 2 \hat { i } + \hat { k } ) + t ( 2 \hat { i } + 2 \hat { j } - \hat { k } ) , t \in \mathbb { R }$
(D) $\vec { r } = t ( 2 \hat { i } + 2 \hat { j } - \hat { k } ) , t \in \mathbb { R }$

Let $L _ { 1 }$ and $L _ { 2 }$ be the following straight lines.
$$L _ { 1 } : \frac { x - 1 } { 1 } = \frac { y } { - 1 } = \frac { z - 1 } { 3 } \text { and } L _ { 2 } : \frac { x - 1 } { - 3 } = \frac { y } { - 1 } = \frac { z - 1 } { 1 } .$$
Suppose the straight line
$$L : \frac { x - \alpha } { l } = \frac { y - 1 } { m } = \frac { z - \gamma } { - 2 }$$
lies in the plane containing $L _ { 1 }$ and $L _ { 2 }$, and passes through the point of intersection of $L _ { 1 }$ and $L _ { 2 }$. If the line $L$ bisects the acute angle between the lines $L _ { 1 }$ and $L _ { 2 }$, then which of the following statements is/are TRUE?
(A) $\alpha - \gamma = 3$
(B) $l + m = 2$
(C) $\alpha - \gamma = 1$
(D) $l + m = 0$

The equation of the line through the point $( 0,1,2 )$ and perpendicular to the line $\frac { x - 1 } { 2 } = \frac { y + 1 } { 3 } = \frac { z - 1 } { - 2 }$ is :
(1) $\frac { x } { 3 } = \frac { y - 1 } { - 4 } = \frac { z - 2 } { 3 }$
(2) $\frac { x } { 3 } = \frac { y - 1 } { 4 } = \frac { z - 2 } { 3 }$
(3) $\frac { x } { - 3 } = \frac { y - 1 } { 4 } = \frac { z - 2 } { 3 }$
(4) $\frac { x } { 3 } = \frac { y - 1 } { 4 } = \frac { z - 2 } { - 3 }$

In coordinate space, $O$ is the origin, and point $P$ is in the first octant with $\overline{OP} = 1$. The line $OP$ makes an angle of $45^\circ$ with the $x$-axis, and the distance from point $P$ to the $y$-axis is $\frac{\sqrt{6}}{3}$. Select the $z$-coordinate of point $P$.
(1) $\frac{1}{2}$
(2) $\frac{\sqrt{2}}{4}$
(3) $\frac{\sqrt{3}}{3}$
(4) $\frac{\sqrt{6}}{6}$
(5) $\frac{\sqrt{3}}{6}$