Why do people usually fly hot-air balloons in summer? [A...
提示:爱丽丝的妈妈病了，爱丽丝想向老师格林先生请几天假。Alice： Excuse me, Mr. Green. 15 d like to take a few days off.Green：___51___ ?Alice： My mother is ill. I have to take care of her.Green：Oh dear! I am sorry to hear that ___...