下列哪种情况更有可能降低学员的学习积极性？ Which would more likelylead studengts becoming frustrated?
A.过于随便地表扬学员 Giving the studengs meaningless praise
B.告诉学员他们的工作不令人满意，但又不解释其原因 Telling studengts their work is unsatisfactory with no explanation
C.当教员不懂，却又极力掩饰自己的错误或欺骗学员时 Covering up instructor mistakes or bluffing when the instructor is in doubt
正确答案是B