句型转换。

1. Mary was able to find the way back home. (改为否定句)

    Mary _______  _______ to find the way back home.

2. I don't know what I should do. (改为同义句)

    I don't know what _______  ________.

3. It took them ten days to finish the work. (对画线部分提问)

    _______  ________ did it take them to finish the work?

4. I'd like to buy some tickets to the wonderful concert. (改为一般疑问句) 

                  you like to buy                tickets to the wonderful concert?

5. The book is too expensive for me to buy. (改为同义句)

    The book is               expensive               I can't buy it.

2010年3月22日，甲建筑工程公司承包乙房地产开发公司的一座高层公寓的建设工程；2010年7月10日，甲公司将玻璃幕墙工程分包给丙建设施工公司；在施工过程中，由于脚手板断裂致使丙公司6名施工工人高空坠落丧生。根据我国《建设工程安全生产管理条例》的规定，此次安全事故应由( )。

A．甲公司承担主要责任
B．甲公司和乙公司共同承担责任
C．丙公司承担主要责任
D．甲公司和丙公司承担连带责任