2. To fold a batch of paper cranes, Student A needs half an hour alone, and Student B needs 45 minutes alone. Therefore, if Students A and B fold together, they will need ( )
A. 12 minutes
B. 15 minutes
C. 18 minutes
D. 20 minutes
2. Solution: $\frac{1}{\frac{1}{30}+\frac{1}{45}}=\frac{\frac{1}{5}}{\frac{5}{6 \times 15}}=18$ (minutes) Answer: C