A．They sell them as a hobby.
B．They make them as a hobby.
C．They use them on their farms.
D．They make and sell them to make a living.

A．How insects breed in extreme desert temperatures.
B．Different types of beetles.
C．Poisonous plant in desert.
D．How beetles can defeat a plant' s defense system.

A．Its resin (树脂) isn't poisonous.
B．It can shoot its resin a great distance.
C．Its leaves have no veins.
D．It doesn't need much water to grow well.