The boy didn't feel completely ________ when he was asked to sing a pop song before the whole class.[      ]

A. in surprise  

B. at ease

C. in danger  

D. at present

水是生命之源，保护水资源，防止水污染是每个公民和全社会的责任。下列做法有利于防止水资源污染的是

①农业生产中要合理使用农药和化肥，提倡使用农家肥 ②工业废水和生活污水处理达标后再排放 ③不用含磷洗衣粉 ④工业上应用新技术、新工艺减少污染物的产生。[ ]

A. ①②④

B. ②③④

C. ①②③

D. ①②③④