铝管焊接后，应用60~80℃的热水冲洗，并用毛刷或铜刷将残渣刷干净。
参考答案：对
—Where's Li Hua?
—Look ! He _____ tennis on the playground.[ ]
A. plays
B. played .
C. was playing
D. is playing
为什么说独立分配规律是杂交育种的重要理论基础？
