问题 选择题

在完成肺泡里的气体交换后,血液(  )

A.由静脉血变成动脉血

B.由动脉血变成静脉血

C.还是静脉血

D.还是动脉血

答案

气体总是从浓度高的地方向浓度低的地方扩散;由于肺泡内氧气的含量比血液中的多,二氧化碳的含量比血液中的少,因此,血液流经肺泡外的毛细血管时,氧气便由肺泡扩散到血液里,同时,血液里的二氧化碳扩散到肺泡里,因此在完成肺泡里的气体交换后,血液由含二氧化碳多、氧少的静脉血变成含氧丰富、含二氧化碳少的动脉血.

故选:A

单项选择题

阅读下列短文,从每题所给的四个选项(A、B、C和D)中选出最佳选项,并在答题卡上将该项涂黑。

B

Grandparents Answer a Call

As a third generation native of Brownsville, Texas, Mildred Garza never pleased move away,. Even when her daughter and son asked her to move to San Antonio to help their children, she politely refused . Only after a year of friendly discussion did Ms Gaf finally say yes. That was four years ago. Today all three generations regard the move to a success,giving them a closer relationship than they would have had in separate cities.

No statistics show the number of grandparents like Garza who are moving closer to the children and grandchildren. Yet there is evidence suggesting that the trend is growing. Even President Obama’s mother-in-law, Marian Robinson, has agreed to leave Chicago and into the White House to help care for her granddaughters. According to a study grandparents com. 83 percent of the people said Mrs. Robinson ‘s decision will influence the grandparents in the American family. Two-thirds believe more families will follow the example of Obama’s family.

“in the 1960s we were all a little wild and couldn’t get away from home far enough fsst enough to prove we could do it on our own,”says Christine Crosby, publisher of grate manazine for grandparents .We now realize how important family is and how important”” to be near them, especially when you’re raining children.”

Moving is not for everyone. Almost every grandparent wants to be with his or her grandchildren and is willing to make sacrifices, but sometimes it is wiser to say no and visit frequently instead. Having your grandchildren far away is hard, especially knowing your adult child is struggling, but giving up the life you know may be harder.

Why was Garza’s move a success?()

A.It strengthened her family ties.

B.It improved her living conditions.

C.It enabled her make more friends.

D.It helped her know more new places.

填空题