以下哪种类型重症肌无力的死亡率最高（）
A.眼肌型轻、中度全身型
B.轻、中度全身型
C.急性重症型
D.迟发重症型
E.肌萎缩型
参考答案：C
The little boy was so careless with his spelling that she often_____ letters from words.
A．left out
B．left behind
C．left off
D．let alone
