New buildings in earthquake-prone areas must be heavily reinforced or else they may otherwise collapse in a strong quake.

A. or else they may otherwise collapse in a strong quake
B. or they may collapse in a strong quake
C. so as not to collapse in a strong quake
D. not to collapse in a strong quake
E. or else it may collapse in a strong quake

Answer:B

I felt that they could be refering to both buildings and earthquake-prone areas. Why is answer choice C wrong?