问两道英语语法选择题1.------yesterday -------- he realized how serious

问两道英语语法选择题
1.______yesterday ________ he realized how serious the problem was.
A.Not until; did
B.It was not until; that
C.It was until; that
D.It was not until; when
A,B是不是都能选?
选A的话是倒装,选B的话是强调句
我说的对么?如果不对,请指点正确答案,并告诉我若要选项正确,应如何改正.
2.It was about 600 years ago__________ the first clock with a face and an hour hand was made.
A.that
B.until
C.before
D.when
我的想法:
在A,D中犹豫.
若A的话,是强调句
若D的话,It was +一段时间+before 句型
请指教~!