昆虫蜕皮是指（ ）
A．蜕掉外骨骼
B．蜕掉皮肤层
C．蜕掉皮肤和骨骼
D．蜕掉内骨骼
昆虫生活在陆地上，为适应陆地干燥的环境，蝗虫的身体表面有坚硬的外骨骼，可以起到保护和支持内部的柔软器官，防止体内水分的蒸发．但外骨骼不能随着蝗虫身体的长大而长大，所以在蝗虫的生长发育过程中，有脱掉原来的外骨骼的现象，这就是蜕皮．可见A、B、C、D四个选项中只有A正确．
故选：A．
| 阅读理解。 | |||
| Dear Mr / Ms, We are very pleased to welcome President William Taylor and Manager James Rogers to Beijing and Shanghai in April for about a week. We offer the following itinerary (行程表) for your consideration.
| |||
| 1. William Taylor and James Rogers will arrive in Beijing on _______. | |||
| A. Sunday B. Monday C. Tuesday D. Wednesday | |||
| 2. They will _______ at 9:30 am on April 19. | |||
| A. arrive at Great Wall Hotel B. have a cocktail party C. visit the Summer Palace D. have a discussion | |||
| 3. Their group discussions will last _______ hours. | |||
| A. 4 B. 5 C. 6 D. 7 | |||
| 4. They will go to Shanghai _______ on Wednesday. | |||
| A. by car B. by train C. by air D. by ship | |||
| 5. The letter is mainly about _______. | |||
| A. a plan of a journey (行程) B. a business meeting C. an important discussion D. a business between two companies |