11． In jazz music, a riff is a simple melodic figure, _________ and repeated several times.
(A) usually one or two measures lasted
(B) lasted one measure or two usually
(C) is lasting one or two measures usually
(D) usually lasting one or two measures
我觉得答案应该是A，很明显独立主格结构，measures做逻辑主语
独立主格结构的特点：
1）独立主格结构的逻辑主语与句子的主语不同，它独立存在。
2）名词或代词与后面的分词，形容词，副词，不定 式，介词等是主谓关系。
3）独立主格结构一般有逗号与主句分开。
The test finished, we began our holiday.
= When the test was finished, we began our holiday.
考试结束了，我们开始放假。
He came into the room, his ears red with cold.
他回到了房子里，耳朵冻坏了。
请讨论
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