It was in 1969 _______ the American astronaut succeeded in l

It was in 1969 _______ the American astronaut succeeded in landing on the moon.
1.It was in 1969 _______ the American astronaut succeeded in landing on the moon.
A.that B.which C.when D.in which
2.Is it in that factory _______ “Red Flag” cars are produced?
A.in which B.where C.which D.that
这两道题为什么填that呢?
有人说是强调句型,可是我还是不明白