5. Let $\mathbb { Z }$ be the set of all integers. Let $A = \left\{ n \in \mathbb { Z } \mid n ^ { 2 } + 10 n + 21 \right.$ is divisible by 7 $\}$. Which of the following statements is/are true? (a) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 0 \bmod 7 ) \}$ (b) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 0 \bmod 7 )$ or $( n \equiv 4 \bmod 7 ) \}$ (c) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 1 \bmod 7 )$ or $( n \equiv 5 \bmod 7 ) \}$ (d) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 2 \bmod 7 )$ or $( n \equiv 6 \bmod 7 ) \}$
5. Let $\mathbb { Z }$ be the set of all integers. Let $A = \left\{ n \in \mathbb { Z } \mid n ^ { 2 } + 10 n + 21 \right.$ is divisible by 7 $\}$. Which of the following statements is/are true?\\
(a) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 0 \bmod 7 ) \}$\\
(b) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 0 \bmod 7 )$ or $( n \equiv 4 \bmod 7 ) \}$\\
(c) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 1 \bmod 7 )$ or $( n \equiv 5 \bmod 7 ) \}$\\
(d) $A = \{ n \in \mathbb { Z } \mid ( n \equiv 2 \bmod 7 )$ or $( n \equiv 6 \bmod 7 ) \}$\\