对于蜗轮减速器中，选用头数为（ ）的蜗杆，减速效果最好。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='24894' and id < 2124490 and id<>'2124490' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='24894' and id > 2124490 and id<>'2124490' order by id asc limit 5