å两天çè§ä¸ä¸ªå¥å,He saw a UFO fiying over his head è¿ä¸ºä»ä¹è½å ing?
é£ä»ä¹æ¶åè½ç¨to do, to have done, to be doing å¢?
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see sb do ï¼è¿éé¢çdo æ¯ä¸å®å¼çç¥äºto,ä¹ä½å®¾è¡¥ï¼è¡¨ç¤ºå®¾è¯åæäºçå
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to have done 表示å¨ä¸»å¥è°è¯å¨è¯ä¹ååççå¨ä½ i am sorry to have troubled you
to be dong 表示å主å¥è°è¯å¨è¯åæ¶åççå¨ä½ she seems to be crying
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那被动语态呢,可以加ed吧
追答可以