单项选择题A．By observing the oldest stars in the universe. B．By studying the nearest stars that can be seen. C．By fixing the age of the oldest stars in the Galaxy.

单项选择题A．15 million dollars.B．50 million dollars.C． 5 million dollars.

单项选择题A．One week.B．One month. C．Two daysD．Three days.

单项选择题A．EggsB．DietsC．ProteinD．Exercises

单项选择题A．Because she believed eggs were not very expensive and also contained a lot of protein. B． Because she thought her heart was strong and eating too much protein could not hurt her heart. C．Because she had been told that eating eggs could help her to have a fine figure. D．Because she liked eggs so much that she could not stand if she didn’t eat eggs every day.