it was in the 29th Olympic Games——were held in Beijing ——China won

问题描述:

it was in the 29th Olympic Games——were held in Beijing ——China won
51 gold medals.
that that
后面的that是强调句吧,但请问前面为什么填that which为什么不成

序数次后面有先行词
必须用that 不用which
this was the first film that I saw.