假设银行准备金率为10%（包括法定准备金和超额准备金），居民和企业的现金与存款比率为20%，如果中央银行计划使货币供给量增加400亿元，以下能够实现中央银行目标的操作是（ ）。

(单选题)为证实养殖场的超级细菌会传播给人类，研究者在某地超市购买了鸡肉和猪肉，从中分离病原菌。同时在该地的医院中选择患有膀胱炎和 (单选题)They believed that by using computers the production of thei (单选题)The matter ( ) your study surely requires ( ) carefull (单选题)I don’t like ( ) bills but when I do get them I like ( (单选题)Fred entered without knocking and, very out of breath, sank (单选题)He wasn’t asked to take on the chairmanship of the society, (单选题)I think he is taking an active part in social work. I agree (单选题)We realized that he was under great ( ), so we took no no (单选题)I hope my school life of senior high will be ( ) than tha (单选题)After the new technique was introduced, the factory produced