The first term of a sequence is 20 .

If a term in the sequence is $t$ and $t$ is even, the next term is $\frac{1}{2} t$.

If a term in the sequence is $t$ and $t$ is odd, the next term is $3 t+1$.

Therefore, the first three terms in the sequence are 20, 10, 5 .

What is the 10th term of the sequence?
(A) 2
(B) 4
(C) 5
(D) 1
(E) 8
The third term is odd $(t=5)$, so the fourth term is $3(5)+1=16$, which is even.

Thus, the fifth term is $\frac{1}{2}(16)=8$, which is even.

Thus, the sixth term is $\frac{1}{2}(8)=4$, which is even.

Thus, the seventh term is $\frac{1}{2}(4)=2$, which is even.

Thus, the eighth term is $\frac{1}{2}(2)=1$, which is odd.

Thus, the ninth term is $3(1)+1=4$, which is even.

Thus, the tenth term is $\frac{1}{2}(4)=2$.

ANSWER: (A)