This is Mike's bedroom. It's new and nice. Today Mike's friends, Tom and Lucy are here, too. They are playing video games. Many things are on the bed. It's messy（凌乱的）. The coat is Mike's. The T-shirt and the socks are Tom's. There is a red cap. It must be Lucy's.

①f为突触前膜，上面的褶皱是由于释放神经递质形成的；

②e属于内环境，当其中的蔗糖含量过低时肌肉不能正常发挥功能；

③d处进行电信号到化学信号的转换；

④e处出现了神经递质也不一定能引起肌肉收缩．

English Around the World

    There are more than 3,000 languages ____（speak）in the world. Of all these languages, English is the most ____(wide) used. Recent ____(survey) show that more than 500 million people speak English as their mother tongue.

    From its roots in England, the language was spread around the world ____English traders and English governments in new lands. One of these new lands ____(become) the United States of America. The population of the United States is 309 million,____ (make) it the country with the ____large) number of native English speakers.

    About 300 million people speak English as their second language. There are even more people, like some in Europe as well as in China and Japan,____ study English as a foreign language.

    English has become the base language for international business, for the world's airlines and even for the Internet. Whatever language people speak, they need  ____(know) some English if they work in these fields.____ is clear that the English language is becoming more important.

根据题意，补全对话。

— Are the vegetables healthy? 

—____ .(做肯定回答)