技术速度
参考答案：是指列车在区段内运行，不包括中间站停站时间，但包括起停车附加时间在内的平均速度。
One of the biggest problems in food production has always been that people have no reliable access to exact information, ____________ is often the case in China.
A．that
B．what
C．which
D．it
Jim is a good son. He never _______ to write to his mother every month.
A．fails
B．misses
C．loses
D．forgets
