To solve the formula [tex]\( C = \pi d \)[/tex] for [tex]\( d \)[/tex], we need to isolate [tex]\( d \)[/tex] on one side of the equation. Here are the steps:
1. Start with the equation:
[tex]\[ C = \pi d \][/tex]
2. To isolate [tex]\( d \)[/tex], we need to divide both sides of the equation by [tex]\( \pi \)[/tex]. Doing so, we get:
[tex]\[ \frac{C}{\pi} = \frac{\pi d}{\pi} \][/tex]
3. The [tex]\( \pi \)[/tex] on the right-hand side will cancel out, leaving us with:
[tex]\[ \frac{C}{\pi} = d \][/tex]
Rewriting this, we find:
[tex]\[ d = \frac{C}{\pi} \][/tex]
Thus, the correct choice among the given options is:
[tex]\[ \boxed{B} \][/tex]
