I almost think you have given up visiting me.(错误)I almost thought you had given up visiting me本句是说话人见到对方到来时说的,他原以为对方不会来看他了。这个“原以为”是以前的说法,所以要将第一句中的“think”改为过去式。由于主句改用过去式,所以从句也得有现在完成时改成过去完成时。