Becky was in the bathroom. She was brushing her _________ and the tap（水龙头）was on. “Turn that tap off,” a voice came out. Becky was scared. She looked around, but saw no one. “Turn off that tap. You are _________ water!”

“Who...who are you?” Becky’s voice was _________.

“I’m a drop of water. Do you know _________ I’m from?”

“From the tap, I think,” said Becky.

“Yes. But a few days ago, I was in a cloud. Then I dropped into a river. The river _________ me to a lake. Then I travelled to your city and it was time to get cleaned up.”

“Get cleaned up?” Becky asked.

“Yes. I was _________ during my journey, so they must clean me up. Then I travelled _________ the pipes（水管）under the ground. I waited there _________ you called me, and here I am. After you’ve finished with me, I’ll go to a sewage plant（污水处理厂）. Then they’ll push me into the river and I’ll go _________ to the sea again.”

“Again?”

“Yes. So remember not __________ me or waste me!”

3 . Blue whales are the largest animals in the world. But they are amazing _______ because of their huge size, but their slow heartbeat.

For the first time , scientists have researched the _______ of a blue whale. They found _______ when blue whales dive (潜水) for food, their heart rates (心率) are as _______ as 2 beats per (每) minute (bpm). Scientists used to _______ that their diving heart rate was 15 bpm. When the whales go to the ocean’s _______ to breathe, their heart rate is between 25 and 37 bpm.

Usually, the larger an animal is, _______ its heart beats, since it takes more time to pump (输送) blood around _______ body. Shrews, the smallest mammals (哺乳动物), have a heart rate of up to 1,000 bpm. Humans usually stay between 60 and 100 bpm.

_______ slowing their heart rate, blue whales can send more blood to the muscles (肌肉) that they use ________. These muscles become stronger, allowing the whales to dive for longer periods of time.