根据句意，用所给单词的适当形式填空。
【小题1】“Help yourselves (you) to some fish．” Mrs．Black said to her guests．
【小题2】Although he is in his nineties (ninety), he can do some farm work and look after himself well．
【小题3】Neil Armstrong took some rock samples for further (far) research．
【小题4】When the parade of Disney characters appeared, all tourists screamed with excitement (excited)．
【小题5】Beijing is in the northern (north) part of our country．
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解析：
【小题1】此题考查固定结构help oneself to sth表示随便吃什么，因her guests是复数，故用yourselves。
【小题2】此题考查固定结构in one’s nineties表示在某人九十的时候，故选nineties.
【小题3】此题考查形容词的比较级，表示更深的研究，故用further或farther。
【小题4】此题考查名词，根据单词的提示，excited的名词形式是excitement。
【小题5】此题考查形容词，此句的含义是北京在我们国家的北方故同northern。