Artificial rainmaking has been most successful in the ______.

A．their abilities and physical strength start to become weak
B．the inherent characteristics of our value system makes it so
C．they don't want to be rejected
D．they have no courage to venture

A．have more job opportunities than young people
B．have new chances to remain active in society
C．live below the poverty line
D．no longer believe in the promise of a happy life upon retirement