问题
选择题
Frank often wears a mask _____ he can keep fit in the foggy and hazy (霾) weather.
A．only if
B．until
C．so that
D．even though
答案
答案：C
题目分析：句意：弗兰克经常戴着面具为的是在雾霾天气他可以保持健康。only if只有；until直到；so that以便; 结果，以致；even though即使，纵然。根据前后分句意思可知该选C.