朋友间相处的礼仪要求包括（）。 A.保持联络 B.坦诚相交 C.择善而交 D.有求必

阅读下面短文，根据短文内容完成下列句子。

     Schools all around the world have their own rules for students. However, perhaps one rule is

common in all lhe schools-students can't chew bubblegum in school.

    But every year on the first Friday in February, many schools in the USA encourage their students to

 "break the rule".  They hope the students can take part in the activity called Bubble Cum Day". The iclea

 of' Bubble Gum Day came from children's book writer Ruth Spiro. He thought it woulcl be cool to have

 lots of children chewing bubble gum and raising money on the same day. The money is often going to

 some charity. Bubble Gum Day turned out to be a sweet success.

    Now Bubble Gum Day is more and more popular in the country. Many people outside school also

 begin to join in the activity. Isn't it great?

1. All sclloo in all over the world have their _____ for students.

2. Bubble Gurn Day is on the first _____ in February in America.

3. _____ got the idea of Bubble Gum Day.

4.  Now Bubble Gum Day becomes very _____ in the USA.

5. Many people _____ begin to join in the activity.

过抛物线x²=4y的焦点F作直线交抛物线于P₁（x₁，y₁），P₂（x₂，y₂）两点，若y₁+y₂=6，则|P₁P₂|的值为[ ]

A.5

B.6

C.8

D.10

地梁的跨度一般为( )m。

A．1～3

B．6～9

C．3～5

D．8～10

读东北地区年降水量分布图（单位：mm），据此回答1~2题

1、影响东北地区年降水量分布的主要因素有[ ]

A、太阳辐射

B、距海远近

C、季风风向

D、纬度位置

2、东北地区平原广大，一首诗歌曾提到“……这里的土地肥到家，插上根筷子会发芽，栽上块柴火也开花……”足见其土壤肥沃。但目前，东北地区土地利用中却存在一些问题，主要是 [ ]

A、黑土土层变薄，肥力下降

B、沼泽地开发，湿地破坏

C、不合理的灌溉，土壤盐碱化

D、过度开垦，土地荒漠化

水泵叶轮切削后，水泵的（）相应降低。

A、流速

B、转速

C、效率

D、流量、扬程、功率