Using india's population pyramids into its hypothetical future, how is it possible for a population to continue growing in several generations after women begin to average 2 children each?

One factor that would make it possible is the decrease in the number of deaths, which could be a result of improved health care. In a country which a very low life expectancy in 1970 (50 years) an increase can be achieved easily with small health improvements and in fact it increased to 65 years since 1970s.

During the paleolithic, hominins grouped together in small societies such as bands, and subsisted by gathering  plants  and fishing, hunting or scavenging wild  animals. the paleolithic is characterized by the use of knapped stone tools, although at the time humans also used  wood  and bone tools.

Ithink the answer you are looking for is (b).