The old man _____ live with his wife, but now he _____ alone after she died. [ ]

A. used to; is used to live

B. used to; is used to living

C. was used to; used to live

D. did use to; is use to live

建设工程开工前，（）单位负责办理工程质量监督手续。

A、施工

B、监理

C、建设

D、监理单位协助建设