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：弗兰克经常戴口罩所以他可以在雾霾天气里保持健康。So that引导结果状语从句，only if表示“只要”；even though表示“即使”，until表示“直到”，故选C。