In one-dimensional motion with constant acceleration and starting from rest, an object travels a distance $d$ in a time $t$. Which expression gives the acceleration $a$ in terms of $d$ and $t$?

• A. $a=\frac{d}{t^2}$
• B. $a=\frac{2d}{t}$
• C. $a=\frac{t^2}{2d}$
• D. $a=\frac{2d}{t^2}$

Answer: (D)