—Once a week.

A

     Birds live in thetrees. Squirrels（松鼠） live in thetrees. But do you know that some frogs（蛙） live in the trees, too? The tree frogis hard to find. It can change colors. On green leaves, it stays green. On abrown branch（树枝），it turns brown. Some tree frogs can change from green to gold（金黄色） or blue.Tree frogs have legs and wide feet. They have sticky pads（黏性的肉趾） at the end of their toes. These sticky toe pads keep the tree frogs from falling off the trees. Tree frogs have different colors and markings（斑点） on their skins. Their eyes are different, too. Some have green eyes, and others have bright red ones.The sounds they make are different, too. One frog makes a sound like a dog barking（狗吠）. Another frog makes a loud noise like a snore（打鼾）.There is evena frog that whistles（吹口哨）！

     A teacher was asking a student lots of questions, but thestudent  1  answer any of them. The teacher then decided  2  him a very easy question so that he could get 3 right.“Who was Beethoven?”she asked. The student answered, “He was American,” after he  4.“ 5. He was a German musician,”the teacher said. She  6a little angry now, but she was trying 7  it. Then she asked,“Who wasthe first president（总统） of the USA?”The student thought 8  a long time, but he didn't say  9.Then the teacher got very angry and shouted,“George Washington!”The student got up and  10  to walk towards the door.“Come back!”the teacher said，“I didn't let you go.”“Oh, I'm sorry,”the student said,“I thought you called the next student.”

—No, ________.