题目

You are supposed to take the medicine only t________ a day. More than that is harmful. 答案：【答案】twice【解析】句意：这种药你应该一天只吃两次。吃多了会有害的。根据“More than that is harmful.”吃多了会有害的。此处是指这种药一天只吃两次。再结合首字母提示可知，填twice；twice a day：一天两次。故填twice。樱桃素有“开春第一果”之称，吃起来酸甜可口．这些酸甜物质主要存在樱桃细胞的（　　）A.细胞核B.液泡C.线粒体D.叶绿体