In the mass extinction 65 million years ago, ______ of all species on earth vanished.

A．old people can easily accept the change
B．people can move from place to place
C．individuals can hardly become innovative
D．economy develops at high speed

A．They need to fulfill more duties.
B．They are incapable of balancing the budget.
C．They have their children spoiled and overindulged.
D．They get empty-handed after divorc