单项选择题
Seldom（）any mistake during his past ten years of service there.
A．did he make B．he made C．he makes D．he did make
单项选择题 There are forty students in our class.（）of them are League members.
单项选择题 By the end of this year, they（）the construction of the subway.
单项选择题 You cannot master a foreign language（）you work hard at it.
