Giotto- advanced art
dante- advanced literature
petarch-advanced humanism
Medici family - growth of florence
We can immediately reject two of the answers: "ameliaration" and "pejoration" as they mean that something has a better (the first) or a worse (the second) meaning -but this is not the case here.
Now, the trend is: something returned>>income>> income from rent
as you see, it has a more and more specialised meaning - the answer is "specialization"
