17 17. a. backwards and forwards b. if someone is up and down, they sometimes feel well or happy and sometimes do not c. to a higher position and then a lower position, several times 起伏,上下波动
up and down
18 18. a. as much or as many as a certain amount or number but not more b. also 又作 for the whole of a period until a certain time or date c. clever, good, or well enough to do something d. if something is up to a particular standard, it is good enough to reach that standard e. doing something secret or something that you should not be doing 正在做〔秘密或不该做的事〕 in questions and negatives
用于疑问句和否定句 | spoken
up to sth up till
24 24. a. available for a particular process b. being considered for election or for a job c. appearing in a court of law because you have been ACCUSED of a crime d. willing to do something or interested in doing something [口]
愿意做某事; 对某事感兴趣 spoken
up for sth