If the circle `x^2+y^2+2ax+8y+16=0` touch x-axis ,` then, t h e value o f 'a' is (a)`+-16` (b) `+-4` (c) `+-8` (d) `+-1`

Explanation

To solve the problem, we will analyze the given equation of the circle and apply the condition for the circle to touch the x-axis.

### Step-by-Step Solution:

1. **Identify the equation of the circle**:
The given equation is:
\[
x^2 + y^2 + 2ax + 8y + 16 = 0
...