These younger volunteers would be familiar with and competent using
technologies such as activity trackers.问:我觉的这个句子是不是错的?be familiar with和 be competent to 是并列的两个短语而此处competent后没有介词 to,有be competent at
doing sth: 在某事/方面有...
我有点搞不清如果before段是过去时,seem部分是该用什么时态?假如前半句我用完成时态,那应该变seem部分还是变to be部分?It have seemd to be a long time before the food came?还是It seems to have been a long time before the food came?