双宾语的句子怎么改被动语态

双宾语是指谓语动词后带有两个宾语,指人的叫做间接宾语,指物的叫做直接宾语.把带有双宾语的句子变成被动语态时如果将直接宾语（物）变成主语,要在间接宾语（人）前加上介词to或for.如果将间接宾语（人）变成主语,则不用添加介词.
例如：He gave me a book.这个句子中me是间接宾语,book是直接宾语.变成被动语态时如果将book变成主语时要在me前加一个介词to.
--->A book was given to me by him.
--->I was given a book by him 间接宾语（人）变成主语,则不用添加介词.
具体加to还是for要根据句型而定,如give 的句型是give sb sth=give sth to sb,所以添加介词to.但buy sb sth=buy sth for sb ,所以添加介词for.
如He bought me a gift---->A gift was bought for me by him.
---->I was bought a gift by him.