You could hear water pipes cracking ____
问题:
You could hear water pipes cracking _____ they _____ because of the cold. [ ]
A. when; burst
B. before; were burst
C. when; were burst
D. before; burst
You could hear water pipes cracking _____ they _____ because of the cold. [ ]
A. when; burst
B. before; were burst
C. when; were burst
D. before; burst