国家对水土保持工作实行预防为主、因地制宜、加强管理、()的方针。
A.全面规划
B.综合防治
C.注重效益
D.加强监督
参考答案:A, B, C
--- Haven’t seen you for ages! Where have you been, anywhere ?
-- I _______ to New York City. I just got back.
A.have been sent
B.was sent
C.had been sending
D.would be sent
某二叉树中度为2的结点有18个,则该二叉树中有______个叶子结点。