泪膜不稳定即泪膜破裂时间低于()
A.5秒
B.8秒
C.10秒
D.15秒
E.20秒
参考答案:C
解析:泪膜破裂时间:正常10~45秒,<10秒为泪膜不稳定。
I really enjoyed your speech, ______ there were some parts I didn't quite understand. [ ]
A. because
B. unless
C. though
D. after
平衡