—Have you decided when to leave for Australia?—Not yet. We set off at the end of this mon

问题补充：

—Have you decided when to leave for Australia?

—Not yet. We set off at the end of this month.

A. must

B. should

C. need

D. may

答案：

A. must

(答案→)B. should

C. need

D. may

解析：must必须，一定；should应该；need需要；may可能，可以。句意：你决定什么时候去澳大利亚了吗？——还没有。我们应该在本月地动身吧。故选B。