A. ask question about safety during the flight B. jump in any circumstances C. carry personal belongings in an emergency D. locate the nearest exit
单项选择题The professor’s findings show that ()
A. our brains shrink as we grow old B. the front section of the brain does not shrink C. seventy-year-olds have better brains than sixty-year-olds D. thinking can slow down the process of ageing
单项选择题If a ring is marked 12K, then the percentage of gold in it is()
A. 12 B. 50 C. 25 D. 24