把一根30米长的水管截成5米和2米两种规格，设截得长为5米的水管x_爱下问搜题

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问题选择题

把一根30米长的水管截成5米和2米两种规格，设截得长为5米的水管x根，长为2米的水管y根，且没有浪费，每种规格的水管至少有一根，则可能的截法种数是（）

A．4

B．3

C．2

D．1

答案

答案：C

填空题

用所给的单词或词组填空。

How many How What
How much How far When

1. —              can we go to Beijing?  —By train.
2. —              do you arrive here?  —At 6:00 in the afternoon.
3. —              is it from Beijing to Canada?  —It's about eight thousand five hundred kilos.
4. —              is the weather forecast, Jenny?  —It's sunny.
5. —              buses are there?   —Ten buses.
6. —              is your sweater?   —It's 50 yuan.

问答题简答题

简述补体系统的生物学功能。