—Look at these tracks. It __________ be a wolf.
—It needn't be. It ________ be a fox.
A. must ; could B. may ; might
C. need ; must D. could ; need
—Look at these tracks. It __________ be a wolf.
—It needn't be. It ________ be a fox.
A. must ; could B. may ; might
C. need ; must D. could ; need
A
第一空的答案要根据答语来判断。“needn't'’的出现表明第一空为“must”。后一空表猜测，可以用could。