Ⅴ. 阅读理解
Boiling an egg just right is often difficult. It's quite common that the egg white gets cooked while the yolk(蛋黄) is still not OK. By the time the yolk is well cooked, the egg white has become rubbery.
Italian scientists found the best way to cook eggs. They call it “periodic(周期的) cooking”. It takes 32 minutes and you need to move the egg between boiling water and $30°\mathrm{C}$ water every two minutes.
The yolk and the egg white are made of different things and cooked at different temperatures,
said Medical News Today. The yolk has most of the vitamins. The egg white has more protein(蛋白质) and water.
The Italian scientists first did tests on a computer to see how heat moves in the egg. The tests found that changing the temperature between $100°\mathrm{C}$ and $30°\mathrm{C}$ can help cook a perfect egg. The next step was to try the idea with real eggs. With special tools and eight taste experts, the scientists compared the results of the new cooking method with those of the common way we make hard-boiled eggs(cooked for 12 minutes) and soft-boiled eggs(cooked for 6 minutes).
The study shows periodic cooking makes both the egg white and the yolk taste best. It is also the best way to help the egg keep the most nutrients(营养物质).

(
C
)18. The writer talks about the difficulty of cooking an egg by
in Paragraph 1.
A. telling stories
B. listing numbers
C. giving examples
D. asking questions
(
D
)19. How long does it take to boil the perfect eggs according to the Italian scientists?
A. 6 minutes.
B. 12 minutes.
C. 20 minutes.
D. 32 minutes.
(
D
)20. The yolk is rich in
.
A. fat
B. water
C. protein
D. vitamins
(
C
)21. What plays an important role in boiling the eggs according to the new way?
A. The cooking time.
B. The quantity(量) of the water.
C. The temperature of the water.
D. The size of the eggs.
(
D
)22. What can be the best title of the passage?
A. What perfect eggs look like
B. Keeping the most nutrients in eggs
C. Searching for best eggs for cooking
D. How to boil perfect eggs