16. There are ten horses numbered $1, 2, \cdots, 10$. The $k$-th horse ($k=1,2, \cdots, 10$) takes exactly $k$ minutes to run one lap around a circular track. Initially, all horses stand at the starting point of the track and start running in the same direction at the same time, each at its own constant speed. It is known that the minimum time $S=2520$ minutes is required for all ten horses to return to the starting point simultaneously. Let the minimum time $t (t>0)$ be such that at least five horses return to the starting point simultaneously. Then the sum of the digits of $t$ is ( ).
(A) 2
(B) 3
(C) 4
(D) 5
(E) 6
16. B.

Obviously, the shortest time for several horses to return to the starting point of the track at the same time is the least common multiple (LCM) of these horse numbers.

To make the LCM of at least five horses as small as possible, we can consider the smallest prime numbers and combine them.
By simple enumeration, we know that the minimum value is
$[1,2,3,2 \times 2,2 \times 3]=12$.
Thus, the answer is $1+2=3$.