杂交是通过将（）个或（）个以上的品种之间进行交配，组合父母亲的优点以提高后代生产水平

long ago people made fires from lightning(闪电)。 But they had to keep the fire burning, for they couldn’t start it again if there was no lightning. Later, they found out hitting two piece of stone together could make a spark (火花). The spark could fire dry leaves. In this way they could make the fire again if it went out. Then people also learned to make a fire by rubbing. They made a hole on a big piece of wood and put a smaller stick into the hole. They turned the stick again and again. After a few minutes they got a fire.

As years went by, people learned other ways to make a fire. Sometimes they used the heat from sun. they held a piece of glass in the right way and made a piece of paper on fire.

About two centuries ago, people began to make matches (火柴). Matches brought people a quick and easy way to make fire. Today matches are still being used, but people have more new ways to make fires. One of them is to use an electric fire starter. Of course an electric fire starter is much more expensive than a box of matches. But it is more useful.

小题1: A spark can _________.

A．fire any leaves

B．burn anything

C．burn dry leaves

D．keep fires burning小题2: We can also get a fire by _________.

A．making a hole on a big piece of wood

B．putting a smaller stick into the hole

C．turning the stick hard for a while

D．doing all the above together小题3: Matches have been used _________.

A．for about two thousand years

B．for about two hundred years

C．since people began to use fire for cooking

D．since people used the heat from the sun.小题4:From this passage we know _______.

A．using matches is the easiest and most useful way to make fires

B．people don’t use matches any more since they had electric fire starters

C．today there are only two ways to make fires

D．some forest fires happen from lightning小题5: Choose the right order of the ways to make fires people got to know _________.

a. with a match

b. from the sun

c. from lightning

d. by rubbing

e. with an electric fire starter.

A．d ,b, c, a, e

B．d, c, b, a, e

C．c, d, b, a, e

D．c, b, d, a, e

女性36岁，晚饭后在散步中被车撞伤，感右下肢疼痛难忍，不敢活动，查BP90／60mmHg，神情痛苦，心肺听诊尚正常，右下肢不动，被动活动可闻骨擦音，右股骨部位压痛，右腿近端肿胀。

急需检查确诊的是（）。

A.头颅CT

B.腰椎正侧位像

C.胸片

D.右股骨X线片

E.心电图

线性组织结构来自于( )系统。

A．民事组织

B．军事组织

C．教育组织

D．环保组织

预应力钢筒混凝土管是在预应力钢筋混凝土管内放人钢管，其用钢材量比钢管省，价格比钢管便宜。其接口为()，承口环和插口环均用扁钢压制成型，与钢筒焊成一体，是一种比较理想的管材。

A、柔性接口

B、刚性接口

C、承插式

D、焊接式

城市生态系统是指特定地域内的人口、资源、环境通过各种相生相克的关系建立起来的人类聚居地或社会、经济、自然的复合体。下列选项中，( )不属于城市生态系统的特征。

A．人为性
B．开放性
C．脆弱性
D．自然性