55．People are always curious because ____.

A．they cannot explain many things 　　　　　　 B．they know nothing about the world

C．they know little about the world 　　　　　　　 D．they want to be scientists

54．A rock cracks _____.

A．in wet regions 　　　　　　　　　　　　　　　　　　　 B．in dry regions

C．at very high or very low temperatures　　 　D．when salty water falls in

53．When you run, your muscles need ____.

A．more nutrition and oxygen 　　B．more signals　 　C．more salt　 　D．water

52．Scientists who work with the biological sciences study____.

　 A．the earth , the oceans and the sky 　　　　 B．man-made things

　 C．plants and animals 　　　　　　　　　　　　　　　 D．ocean water

51．According to the passage, which of the following statements is true?

　 　 A．People are curious in the same way.

　 　 B．People in different countries are interested in different things.

　 　 C．Men and women are curious about different things.

　 　 D．People of different ages are interested in different things

44．A．appreciate　　　　　 B．stop　　　　　 　 C．hate　　　　　　　　　　 D．forbid

43．A．so　 　　　　　　　　　 B．nor　　　　　 　 C．not only　　　　　　　 D．if

42．A asked　 　　　　　　　　 B．heard　　　　　 C．worried　　　　　　　 D．learned

41．A moving　 　　　　　　　 B．shown　　　　 C．facing　 　　　　　　 D．offered