1.the music is often heard

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同学你好,答案依次是：AB能.
如:He was seen e into the book store就是错的
He was seen to e into the book store正确.
在主动语态中,有时可以加不带to的不定式作宾语.但如果变为被动语态时,则要将省略的to还原.当然这些动词还可以加动名词作宾语,如:I saw him ing into the bookstore变为被动语态则没有变化:He was seen ing into the bookstore.
第三个给你例子理解,比如：1、Being defeated is not a shame2、A dog was lying on the ground,being hit by a car.希望对你理解有帮助、呵呵