Please return ---- two hours.I will be ready ---- then.

题目

Please return ---- two hours.I will be ready ---- then.
A.in till
B.in by
说明原因,

答案

B
in two hours在两小时之内
by then 到那时
till then 要和not连用
如：I won't be ready till then.我到那时才能准备好