在练习过程中，其成绩时而下降，时而提高的现象叫（ ）。

(单选题)42. （ ） (单选题)41.（ ） (单选题)40.（ ） (单选题)39. （ ） (单选题)38.（ ） (单选题)37. （ ） (单选题)______ I arrived earlier, I could have caught that bus. (单选题)If we ______ hard in the past few years, things ______ to sm (单选题)Hardly ______ when a student came to visit her. (单选题)My mother thought I can’t take care of myself, so she didn’t