阅读理解。
Doing experiments can be interesting, and you may try the following experiments at home.
Make sure that you’ll do them with an adult.
1. How many experiments are there in the pictures?
A. Six.
B. Five.
C. Three.
D. Two.
2. The following are the instructions on how to do “Step 2” in these experiments. Which one is the right order?
a. Pour 3/4 of the water away. b. Put a balloon on the bottle.
c. Put the bottle in a bucket of hot water. The air rises into the balloon.
A. a, b, c
B. a, c, b
C. b, a, c
D. c, a, b
3. What can you see in the bottle at last in Experiment A?
A. Some ice.
B. Some water.
C. Some ice and water.
D. A cloud and some water.
4. What will happen to the balloon in “Step 3” in Experiment C?
A. It will be bigger.
B. It will be broken.
C. It won’t change.
D. It will be in the bottle.
冠折，露髓，
折断面至龈下2．5mm，X线片显示，
折断面平齐龈缘，根长11mm，