When I talked with my grandma on the phone, she sounded weak, but by the time we up, her voice had been full of life
A. were hanging
B. had hung
C. hung
D. would hang
网友回答
A. were hanging
B. had hung
(答案→)C. hung
D. would hang
解析：考查时态。By the time 后的从句中多用一般现在时和一般过去时。根据该题的语境可以断定答案为:C