With a determiner:—Have you seen Tom and Mary? —I have not seen 1of them.
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【正确答案】 1、正确答案：either    
【答案解析】解析：neither，either，both仅用于表述两者的情况，而any和all用于表述多者的情况；I have not seen either of them—I have seen neither of them。答案为either。