B. oneIf you need a bike, I'll lend you one. 这句子的原意是: If you need a bike, I'll lend you a bike.不过,由於英语修辞手法切忌重复使用同一个词,所以不会在一句说两次 a bike. One 在这里是个代词,代表前面述及的物件(单数),即 a bike。若然前面的宾语是众数的话,後面就会用 some.If you want to decorate the room with flowers, I will get you some....