精子的头部主要由下列（ ）构成。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='29831' and id < 2422470 and id<>'2422470' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='29831' and id > 2422470 and id<>'2422470' order by id asc limit 5