这里up 是 out of bed:to get up 的 意思
比方：
How come you are still up?‎ .Why are you still up and not in bed asleep?‎天哪 那这题真难 看了半天没看懂 买一赠一啦再问你一个问题____ most of us keep right on touching things as we grow up.选项中同时出现了though 和 yet（联系上下文应该是转折的意思） 为什么答案选yet而非though呢？yet 在字典里有很多意思。要根据上下文。。。Adv （副词）1. At this time; for the present: 目前。如：。。。isn't ready yet. 还没准备好。2. Up to a specified time; thus far: 迄今。如：。。The end had not yet come. 尚未到最后。3. At a future time; eventually: 在将来某个时间，最终。 如：。。。may yet change his mind. 还可能改变主意。4. Besides; in addition:此外，除了如：。。。 returned for yet another helping. 返回又一次帮助。5. Still more; even: 更/甚至 如：。。。a yet sadder tale. ：更悲哀的故事。6. Nevertheless: 不过。 如：。。。young yet wise. 年轻但明智。conj. 连词。And despite this; nevertheless: 尽管/不过She said she would be late, yet she arrived on time. 她说她会迟到，但她却准时到达了。