问题
选择题
Water ____ be changed into vapour but it ____ be heated to its boiling point .
A．may ; can
B．can ; must
C．may ; needn''t
D．must ; may
答案
答案：B
can表示可能性，must必须，表示条件。
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Water ____ be changed into vapour but it ____ be heated to its boiling point .
A．may ; can
B．can ; must
C．may ; needn''t
D．must ; may
答案：B
can表示可能性，must必须，表示条件。