单项选择题 （）can never be guaranteed by material things，no matter how expensive they might be.

单项选择题 It is believed that diamond stands for （）love.

单项选择题 Obesity drastically（）among the wealthy and the newly-born middle class.

单项选择题 The doctor couldn’t explain the （）of the high temperature.

单项选择题 It has been believed that cowboys（）a simpler way of life and freedom without restraint.