单项选择题
A．keep sugar and salt in water B．drink it as often as necessary C．take it as much as possible D．use it to kill the bacteria
A．the life-saving ways are medically effective B．their parents are rich enough for the life-saving techniques C．the life-saving techniques are easy to use D．their parents learn the life-saving techniques
A．writing letters B．playing games C．doing business D．all of the above