问题
ked down the hills, _______ softlyto himself
A:had not been heard of
B:has not been heard of
C:had not heard of
D:has not heard of
B:has not been heard of
C:had not heard of
D:has not heard of
正确答案是：
同类题型
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Tom was so careless with his spelling that he often _______letters from words.