屏气试验是粗略测定心功能的简单方法，正常人可持续多少秒（s）以上（）
A.10s
B.30s
C.40s
D.50s
E.60s
参考答案：B
自信的人不承认、自已的失败和不足，只要自己努力就行。[ ]
I spent the whole day repairing the car. The work was______ easy.
A．nothing but
B．something but
C．anything but
D．all but
