单项选择题
A．By selling services that make life comfortable. B．By selling land containing oil. C．By selling public lands. D．By selling coal and other natural products.
A．It can be cooked in many ways. B．It is delicious but inexpensive. C．It gives higher yields than other grain crops. D．It grows easily in various conditions.
A．He didn’’t like physics any more. B．His eyesight was too poor. C．Physics was too hard for him. D．He had to work to support himself.