单项选择题

According to the passage, which of the following should be encouraged to enhance the learning of math and science
1. Problem solving. 2. Actual research. 3. Repetitive in-class drills.
4. Group work. 5. Rote learning.

A.1 and 3.
B.1, 2 and 4.
C.4 and 5.
D.2, 3 and 5.