In the following questions, some of the words have been left out. First read the passage over and try to understand what it is about. Then fill in the blanks with the help of the alternatives given.

A modern exampl e of the proce ss of evolution by natural selection in action is provided by the peppered moth. The moth is .... $(1)$....pale in colour, a mottled grey which . .. . $(2)$ . . .. the moth to sett le, wings outstretched, .... $(3)$ .... the bark of lichen covered trees and .... $(4)$....unnoticed. It can thus save itself from many .... $(5)$ .... birds. However, many years ago some British .... $(6)$ .... found that there does exist a second.
$(6)$