People living in the desert choose to keep their ancient lifestyles and customs, _______people in cities throw away their cultural traditions.

People living in the desert choose to keep their ancient lifestyles and customs, _______people in cities throw away their cultural traditions.

A．when            B．if                C．unless            D．while

People living in the desert choose to keep their ancient lifestyles and customs, _______people in cities throw away their cultural traditions.

1. A.
   when
2. B.
   if
3. C.
   unless
4. D.
   while

 People living in the desert choose to keep their ancient lifestyles and customs, _______people in cities throw away their cultural traditions.

A. when       B. if      C. unless      D. while