3. In the sequence $\left\{a_{n}\right\}$, $a_{2}=3, a_{3}=6, a_{n+2}=a_{n+1}-\frac{1}{a_{n}},$ the value of $a_{5}$ is ( ).
A. 12
B. 24
C. $\frac{11}{4}$
D. $\frac{11}{2}$
3. D. Since $a_{2}=3, a_{3}=6, a_{4}=6-\frac{1}{3}=\frac{17}{3}$, so $a_{5}=\frac{17}{3}-\frac{1}{6}=\frac{11}{2}$.