练习：
1. What is Alvin?
A A research institute.
B A transporting vehicle.
C A submersible.
D A scientist.
2. Which of the following statements is NOT a fact about Alvin?
A h can carry explorers as deep as 6，500 meters.
B It has played a key role in various important undersea expeditions
C It was launched in the sixties of the twentieth century.
D It has been used for more than 40 years.
3. “...a world that is still full of mysteries” refers to
A the earth.
B out space.
C the ocean.
D Mars.
4. In what aspects are the new HOV and Alvin similar?
A Size.
B Speed.
C Capacity.
D Shape.
5. In what aspects are the new HOV and Alvin different?
A Offering better views.
B Speed.
C Size.
D Both A and B.