Some bacteria are able to grow in streptomycin containing medium due to (a) natural selection (b) induced mutation (c) reproductive isolation (d) genetic drift.
Option A Normally bacteria cannot survive in antibiotic containing medium but if it does so it must have acquired resistance against that antibiotic. These are well adapted to grow in streptomycin containing medium and thus are more evolved. So due to natural selection only the more evolved and better adapted species is able to survive.
