I watched him _____ he disappeared from the sight in the distance.

问题描述:

I watched him _____ he disappeared from the sight in the distance.
A.Since
B.After
C.Until
D.Because
_____ I admit that problems are difficult ,I do not agree that they can not be solve.
A.While
B.Suppose
C.Because
D.Until
这两道题一点思路都没有,奇奇怪怪的,请高人指教,

c until 我看着他直到消失在远方
until 直到.为止的意思
while 有虽然得意思,虽然我承认这问题有些难,但我不认为解决不了.