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

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