3句定语从句1.In the office I never seem to have time until 5:30 p

3句定语从句
1.In the office I never seem to have time until 5:30 p.m.,____many people have gone home.
A.whose time B.that C.on which D.by which time
2.In the office I never seem to have time until after 5:30 p.m.,____many people have gone home.
A.whose time B.that C.at which D.by which time
3.By the time____he was 12 years old,he had built a lab of his own.
A.that B.in which C.which D.by which
非限制性定语从句怎么可以用that的