题目内容：

    I remember my hardest homework was in science. I had to make a small  ___________of a cell（细胞）. Science is one of my favorite subjects, but I am not that good at  ___________things.

___________, I used clay（陶土）. I made the clay into a ball, and cut off the top. This was to be the “cell  _______________”. The problems began quickly. The “cell” broke into pieces every time I put my hand on it, and turned to mud every time it got  ___________. It wasn’t working.

So, I used cement（水泥）to make a new cell wall. This one was strong, but it  ___________had problems.

First, it was the size of a basketball and was very heavy. It would be hard to ___________. Second, I couldn’t___________ the other parts of the cell on to the cell wall – the cement was too hard. Third, I wanted to use the tape to give___________ to the parts, but it would not stick to the cement.

There was  ____________I could do about the first problem. ____________the second problem, I put a wire（金属丝）around the cell wall and I used glue to stick parts on to it. Instead of tape, I used paint to name the  ____________.

There was one more  ____________. The cell had to be full of clear water, like a real cell. I filled it with water and brought it to school, but soon the table was wet. I checked, and the cell had a____________in it.

That day, I got a B+ for my  ____________. Although my cell didn’t look good, my teacher could tell how hard I’d worked. Today, as a teacher myself, I keep the model in my classroom as a reminder that hard work should be rewarded（奖励）.

1.A.picture B.example C.model D.part

2.A.making B.shaping C.inventing D.dealing

3.A.At once B.At first C.At last D.At least

4.A.door B.floor C.wall D.material

5.A.wet B.clear C.hard D.strong

6.A.instead B.already C.also D.only

7.A.play B.fill C.take D.carry

8.A.move B.fix C.draw D.see

9.A.answers B.cover C.names D.choices

10.A.something B.nothing C.anything D.everything

11.A.For B.As C.In D.To

12.A.cell B.parts C.wire D.model

13.A.problem B.mistake C.feeling D.change

14.A.card B.hole C.hit D.rock

15.A.homework B.show C.exam D.report