What does Jack Ma think is the difference between those people such like Bill Gates(比尔.盖茨), Jack Welch(杰克.韦尔奇),Larry Page(拉里.佩奇),Warren Buffett(沃伦.巴菲特),Mark Zuckerberg(马克.扎克伯格) and other people?
A.
They are always optimistic for the future.
B.
They never complain.
C.
They always try to solve the problems of the others.