Answer:
A
Step-by-step explanation:
Hello :)
This question is asking us what we can safely conclude when looking at the cause and effect relationships.
Since factories were built in cities, the population in it grew.
This means that more people in the city probably came to the factories to work, since they were built there, hence why the population grew. B is wrong, and C and D doesn't relate since nowhere in the relationship was talking about popularity of factories; only that it helped boost population.