第三部分：阅读理解（共20小题，每题2分，满分40分）
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。
At the age of sixteen, I joined a volunteer group with my dad. I went on my first volunteer project in West Virginia. On the night we arrived, we discovered that “our family” was living in a trailer(拖车) that was in poor condition. A crew had been working on it for two weeks, but every time they finished one problem, another surfaced.
We decided the only reasonable solution was to build a new house – something unusual but necessary under these circumstances. The family was overjoyed with their new house that was twenty by thirty feet with three bedrooms, a bath and a kitchen.
On Tuesday of that week, while we ate lunch together, I asked the family’s three boys, Josh, Eric and Ryan, "What do you want for your new room?" Expecting toys and other gadgets that children usually ask for, we were surprised when Josh responded, "I just want a bed."
The boys had never slept in a bed! They were accustomed to plastic mats. That night we had a meeting and decided that beds would be the perfect gift. On Thursday night, a few adults in our group drove to the nearest city and bought beds and new bedding.
When we saw the delivery truck coming, we told the family about the surprise. We could hardly contain ourselves. It was like watching excited children on Christmas morning.
That afternoon, as we fitted the frames of the beds tog tether, Eric ran into the house to watch us. Too dirty to enter his room, he observed with wide-eyed enthusiasm from the doorway.
As my father slipped a pillowcase onto one of the pillows, Eric asked, "What is that?"
"A pillow," she replied.
"What do you do with it?" Eric continued to ask.
"When you go to sleep, you put your head on it,” I answered softly. Tears came to our eyes as she handed Eric the pillow.
"Oh . . . that's soft," he said, hugging it tightly.
Now, when my sister or I start to ask for something that seems urgent, my Dad gently asks, "Do you have a pillow?"
We know exactly what he means.
56．The writer’s first volunteer project was .
A．working on a poor trailer B．helping a poor family
C．donating beds and bedding D．dealing with a housing problem
57．On bearing Josh’s answer, the writer was shocked because .
A．the family lived in a trailer B．he expected to get some toys
C．he didn’t know what a bed was D．the boys had no bed to sleep in
58．From the passage, we can learn that Eric had never seen before.
A．a trailer B．a truck C．a pillow D．a house
59．By saying “Do you have a pillow?”, the writer’s father means that .
A．what they want to get may be unnecessary
B．they should not waste money on small things
C．they should do more volunteer work for the poor
D．what he will buy is not what they want but a pillow
、电荷量为
的粒子以初速度
垂直电场线进入由两带电平行金属板所形成的电场中，粒子的重力不计，飞出平行板时侧移距离为
，已知两板间的距离为
，电压为
，如图所示。现撤去电场，在原电场区域内加一与纸面垂直的磁场，使带电粒子以同样的初速度从同样的位置进入，又从同样的位置飞出，则此磁感应强度的大小是多大?