For an arithmetic sequence $\left\{ a _ { n } \right\}$, the sum of the first 9 terms is 27, and $a _ { 10 } = 8$, then $a _ { 100 } =$ (A) 100 (B) 99 (C) 98 (D) 97
A company's shuttle bus departs at 7:30, 8:00, and 8:30. Xiaoming arrives at the bus station between 7:50 and 8:30 to board the shuttle, and his arrival time is random. The probability that his waiting time does not exceed 10 minutes is (A) $\frac { 1 } { 3 }$ (B) $\frac { 1 } { 2 }$ (C) $\frac { 2 } { 3 }$ (D) $\frac { 3 } { 4 }$
If $a > b > 1 , ~ 0 < c < 1$, then (A) $a ^ { c } < b ^ { c }$ (B) $a b ^ { c } < b a ^ { c }$ (C) $a \log _ { b } c < b \log _ { a } c$ (D) $\log _ { a } c < \log _ { b } c$
A circle with the vertex of parabola $C$ as its center intersects $C$ at points $A , B$, and intersects the directrix of $C$ at points $D , E$. If $|DE| = 2 \sqrt { 5 }$, then the distance from the focus of $C$ to the directrix is (A) 2 (B) 4 (C) 6 (D) 8