题目

在下列各句的空白处填入一个适当的词，使句子意思完整，语法正确。【1】You'd better change the __________ of staying up late. Remember: early to bed, early to rise.【2】For students, getting good grades isn't __________.They should also learn some life skills.【3】Double Eleven Day has become a time for buying cheap things __________ in China.【4】Because the final examination is coming, my parents don't __________ me to watch TV at all.【5】There is no need to admire others, Tom. You have your own advantages. Just be __________. 某公司一年购买某种货物400吨，每次都购买吨，运费为4万元/次，一年的总存储费用为万元，要使一年的总运费与总存储费用之和最小，则=             吨。