组成核酸的基本结构单位是（    ）

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SQL Error: select id,body,options from ***_enewstiku where sourceid='27524' and id < 2270977 and id<>'2270977' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='27524' and id > 2270977 and id<>'2270977' order by id asc limit 5