All you have to do is read the first 4 sentences then you will find your answer
Erie has 100 000 people, and Pittsburgh has 300 000 - so from the first two Pittsburgh is the bigger one.
Philadelphia has 1.5 million people living in it - it is also the biggest city in Pennsylvania (this is the state where all the cities are) - and this is also the correct answer!
It is not the capital however, as it's Harrisburg.
Answer:
Its a unprecedented increase in agriculture in britain due to increases of labor and land productvity.
