照二归精
参考答案：近代学者黄侃首先提出，中古的照、穿、床、审四母的二等字在上古读作齿头音精、清、从、心母字。
Just call me whenever you are in trouble ______ I'll come to help you immediately. [ ]
A. but
B. so
C. or
D. and
粘性
