3. Four students, A, B, C, and D, participate in the $4 \times 100 \mathrm{~m}$ relay race at the school track and field meet. If the four students are arranged in any order, then the probability that A exactly hands the baton to B is $($ ).
(A) $\frac{1}{4}$
(B) $\frac{1}{6}$
(C) $\frac{1}{8}$
(D) $\frac{1}{12}$
3. A.

By listing or drawing a tree diagram, we can know that there are 24 possible orders for the four students' competition, among which, the cases where Jia hands over to Yi are 6. Therefore, the required probability is $\frac{6}{24}=\frac{1}{4}$.