题目内容
14.---Could you join us this afternoon?---Sorry,I _______.I take care of my little sister because my mother is out.( )
| A. | can't; may | B. | couldn't; have to | ||
| C. | can't; have to | D. | couldn't; may |
分析 --今天下午你能加入我们吗?
--对不起,我不能.我不得不照顾我的妹妹,因为我妈妈出去了.
解答 答案:C.考查情态动词.句意"--今天下午你能加入我们吗?--对不起,我不能.我不得不照顾我的妹妹,因为我妈妈出去了.".could 开头的一般疑问句表示语气更加委婉礼貌,不表示一般过去时态,所以否定回答仍然用can't,不用couldn't.第二个空,根据因为我妈妈出去了,可知不得不照顾我的妹妹,用have to.答案是C.
点评 情态动词无人称和数的变化;不能单独使用,必须与其后的动词原形构成谓语.否定形式通常在后面加not.要注意情态动词的不同用法.
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