To find the circumference of a circle, you can use the formula:
\[ C = \pi \times d \]
where \( C \) is the circumference and \( d \) is the diameter of the circle.
Given that the diameter of the shipping drum is 20 inches, we can substitute that value into the formula along with \( \pi \approx 3.14 \):
\[ C = 3.14 \times 20 \]
Calculating this gives:
\[ C = 62.8 \text{ inches} \]
Therefore, the answer closest to the circumference of the base of the shipping drum is:
D. 62.8 inches