You're ________ your time trying to persuade him；he'll never join us．
A.spendingB.wastingC.losingD.missing在线课程B
该题应从trying着手考虑，其搭配应从A和B项中产生，spend time doing sth．是花费时间做某事，waste time doing sth．是浪费时间做某事，再由he'll never join us可知waster time doing sth．最佳。