Someone called me up in the middle of the night, but he hung up ______ I could answer the phone.

Someone called me up in the middle of the night, but he hung up ______ I could answer the phone.

A．as               B．since　　         C．until　　          D．before

Someone called me up in the middle of the night, but he hung up ____ I could answer the phone.

  A. as           B. since          C. before         D. until

Someone called me up in the middle of the night, but he hung up ________ I could answer the phone.

[　　]

Someone called me up in the middle of the night, but he hung up ________________ I could answer the phone.

A. as　　　　　　　　　　　　    B. since　　　　　　　　　　    C. until　　　　　　　　　　　　　　    D. before