According to who? Not you, you don't have a background in architecture. You must ride on the credentials of someone who does have a background in architecture, here.

These two sentences can be combined together. That would partially solve the ambiguity issue that the other annotation talks about.

When in the 20th century? How far apart? Why is this important to architecture? Why the 20th century? Why focus on this particular time period?

Right now this sentence stands alone, and there isn't enough context to justify it being there.

Canbe combined into one phrase. Does not need to be separated into two parts.

Also, why both politics and economics? Is it really necessary to talk about both in one paper? You only have 3000 words to talk about it. Doing both may be a bit of a reach in terms of scope.

*It's part of the reason why your sentence is so long.

Not quiet "combined". You should be using content analysis to analyse the images.

"architecture" - does not need to be plural

This first sentence is quite the run-on sentence. It can be reworded to something much more concise.

"economics"

Use a comma here, instead of two 'and's

Don't need a comma here.