$\text{Assertion (A)}$: The direction ratios of line $L_1$ are $2, 5, 7$ and those of line $L_2$ are $\frac{4}{\sqrt{19}}, \frac{10}{\sqrt{19}}, \frac{14}{\sqrt{19}}$. The lines $L_1, L_2$ are parallel.
$\text{Reason (R)}$: The direction ratios of a line $L_1$ are $a_1, b_1, c_1$ and those of another line $L_2$ are $a_2, b_2, c_2$. The lines $L_1$ and $L_2$ are parallel if $a_1 a_2+b_1 b_2+c_1 c_2=0$.
The correct option among the following is

• A
  $(A)$ is true, $(R)$ is true and $(R)$ is the correct explanation for $(A)$.
• B
  $(A)$ is true, $(R)$ is true but $(R)$ is not the correct explanation for $(A)$.
• C
  $(A)$ is true but $(R)$ is false.
• D
  $(A)$ is false but $(R)$ is true.