英语帝进来解道英语题,急两道冠词题,第一道the diet is measured in ＿calories,while

英语帝进来解道英语题,急
两道冠词题,第一道the diet is measured in ＿calories,while the food is sold by ＿pound 第二道the cost of this product is calculated by ＿weight 第一道答案为 不填 the 第二道答案为不填 我不明白为什么有的填the有的不填the,按道理是度量单位前加the表每一?那为什么calories前不加the,pound前加the,weight前不加the呢?
第一道答案为第一空不填，第二空填the