青稞灌溉定额是指青稞生长期内灌溉需水量的总和，通常用灌水的水层深度来衡量，下图示意我国部分地区青稞灌溉定额的空间分布，读图完成下列各题。

    Two farmers were on their way home one evening after a hard day's work．Both were tired．They happened to look up at the sky and saw a black cloud overhead．
    "Ah!" said one farmer, "tomorrow we shall have rain and the rice will grow well．" The second answered, "Nonsense （胡说）, the rain will only kill the crops （庄稼）．"
    So they began to fight．Just then a third farmer came along and asked them why they were quarreling（争吵）．Both farmers explained about the black cloud．
    "What cloud?" asked the third farmer．They all looked at the sky．The cloud was no longer there．

如图为空气成分示意图（按体积计算），其中“a”代表的是（　　）

常识填空

      曹操是小说《____》中的人物；“王熙凤”是小说《____》中的人物。