食管的第二狭窄在（）
A．起始处
B．穿膈处
C．与左主支气管交叉处
D．与右主支气管交叉处
E．与胃相接处
参考答案：C
切焦水质不合格的原因？
They want to know ______do to help us.
A．what can they
B．what they can
C．how they can
D．how can they
