单项选择题
A．rats have clever leaders B．rats are clever than men C．rats steal men's food D．rats killed hundreds of millions of men
A．take men's food B．live in cities and villages C．know how to identify poison food D．all of the above
A．we should think out good ideas to kill rats B．we should rather leave the earth than kill the rats C．rats with diseases are the most dangerous enemy of human beings D．rats bring about horrible diseases