To solve the equation \( 9x + 16 = 6x + 1 \), we can start by isolating \( x \). Here are the steps:
- Subtract \( 6x \) from both sides of the equation:
\[ 9x - 6x + 16 = 1 \]
- This simplifies to:
\[ 3x + 16 = 1 \]
- Next, subtract 16 from both sides:
\[ 3x = 1 - 16 \]
- This simplifies to:
\[ 3x = -15 \]
- Now, divide both sides by 3:
\[ x = -5 \]
Thus, the solution is:
\[ \boxed{-5} \]
The answer is D. \( x = -5 \).