Find ways to praise your children often, _____ you'll find they will open their hearts to you. [ ]

A. till

B. or

C. and

D. but

煤中含氧官能团的稳定性顺序为（）。

A.-OH＜C＝O＜-COOH＜-OCH3

B.-OH＞C＝O＞-COOH＞-OCH3

C.-OH＜C＝O＜-COOH＜-OCH3

D.-OH＜C＝O＜-OCH3＜-COOH