__experiments on the laboratoy,it started to rain heavily.A,while performing B,performing C,w...__experiments on the laboratoy,it started to rain heavily.A,while performing B,performing C,while i was performing D,to perform 理由是前后主语不一致,这也能解释得通.可这样不是就有两个谓语了吗（was 和 started ）.如果按以下这道题分析这个题,不是该选B或A吗：Some students ran back to the dormitory ,magezines___under their arms.A.to be held B.was heldC.held D.holding分析：此问题只有一个逗号为简单句,所以只能有一个谓语动词,前面已经有ran作谓语了,.因此空格内只能
__experiments on the laboratoy,it started to rain heavily.A,while performing B,performing C,w...
__experiments on the laboratoy,it started to rain heavily.
A,while performing B,performing
C,while i was performing D,to perform 理由是前后主语不一致,这也能解释得通.可这样不是就有两个谓语了吗（was 和 started ）.如果按以下这道题分析这个题,不是该选B或A吗：Some students ran back to the dormitory ,magezines___under their arms.
A.to be held B.was held
C.held D.holding
分析：此问题只有一个逗号为简单句,所以只能有一个谓语动词,前面已经有ran作谓语了,
.
因此空格内只能使用非谓语动词
你可能没注意到2道题的最重要的差别在第一题有一个连词while，第二题没有任何连接词。这就是非常关键的。 有连接词，说明是2个分句，既然是2分句，都有各自的谓语动词was, started. 然后后面这个句子，无连接词，说明是一个简单句，当然只有一个谓语动词ran, 那么后面的是独立主格结构，所以也就不能用谓语动词，只能用非谓语动词，doing,to do, done，此题是杂志被夹在胳膊下，用的是done----held.
一个谓语动词是 指 一个从句或主句,在没连词的情况下只能有一个谓语动词.第一个句子 选C while i was performing 这是个时间状语从句,里面必需要有一个谓语动词第二个句子 some students ran back to the dormitory,...