Is it to hold the 2010 World Exhibition _______ makes Shanghai the focus of the world?

Is it to hold the 2010 World Exhibition _______ makes Shanghai the focus of the world?

1. A.
   when
2. B.
   that
3. C.
   which
4. D.
   what

Is it to hold the 2010 World Exhibition _______ makes Shanghai the focus of the world?

A. when　        B. that               C. which　            D. what

Is it to hold the 2010 World Exhibition _______ makes Shanghai the focus of the world?

A. when　          B. that                    C. which　                 D. what

Is it to hold the 2010 World Exhibition _______ makes Shanghai the focus of the world?