A．One hour after meal．
B．Immediately after meal．
C．Half an hour before meal．
D．Two hours after meal．
A．Keep practicing until you can do them．
B．Skip such difficult poses．
C．Ask your teacher for help．
D．Change them so that you can do them．
A．Greenhouse gases．
B．Over-exploitation of the beach．
C．Change of agricultural zones．
D．Change of climates．