Scientists smiled as the three young whales swam through the ocean, turning over, jumping, and racing one another in circles around the ship. After spending seven months in a 60,000 gallon (228,000-liter) pool at the New England Aquarium（水族馆）in Boston, Mass, the whales were now free.
The pilot whales, named Notch Small, and Tag, had been staying at the pool ever since they were saved after running aground on a Cape Cod beach in Massachusetts last December. Although about 60 other whales died during that running aground the three young whales were saved and
nursed back to health. Last June, the whales were freed from a ship about 120 miles (152 kilometers) off the coast of Massachusetts. When the three whales finally swam away from the ship. scientists on board cheered. The event, say the biologists, marked the first time that a group of whales has been saved, cared for , and freed back into the wild.
No one knows what causes whales to run aground. Some biologists think that gently sloping beaches may upset the whales’ sonar systems（声纳系统）. Whales find schools of fish and other objects by bouncing sonar waves off the objects. When a whale approaches a gently sloping beach, the sonar waves may bounce away（反弹）from the whale instead of toward it. The whale may end up in shallow water and run aground.
Other experts think a leader of a group of whales becomes ill and beaches itself. Because whales often band together, other whales soon follow, running aground as well.
1．After spending seven months in a pool the pilot whales, named Notch. Small and Tag, were freed in .
A．autumn B．spring C．winter D．summer
2．The scientists in saving, caring for and releasing into the wild any grounded whales before this event.
A．had been successful
B．had never been successful
C．had even been successful
D．had once been successful
3．Some scientists believe that once the leading whale in a group falls ill and runs aground, .
A．others may band together
B．others may fall ill, too.
C．others will not care for it and run away
D．others will follow and beach themselves, too.
4．When a whale approaches a gently sloping beach, .
A．it may be able to send out sonar waves
B．its sonar waves may not bounce back to it
C．its sonar waves may disappear
D．its sonar waves become stronger
5．The underlined words band together in the last Paragraph means .
A．unite in a group B．bite together
C．fight together D．dance together