茶叶中水溶性灰分测定，要求同一样品两次测定值之差为( )。
A．＜0.2%
B．＜0.3%
C．＜0.5%
D．0.2%～0.5%
参考答案：A
The school year is divided into two semesters, __________is September through December.
A．the first of which
B．the first of them
C．the first of it
D．the first of that
输入动物、动物产品、植物种子、种苗及其他繁殖材料，应在( )前办理检疫审批手续。
A．合同签订
B．货物装运
C．货物报检
D．货物报关
