最小费用线路法能使总费用降低，允许有些货物进行返程运输。
参考答案：对
Do you know by the time you leaves school your parents ________ $ 6 000 on your education.
A．will have spent
B．will spend
C．will be spending
D．have spent
树木栽培如采用大苗时，应尽量注意什么？
