Answer:
The answer is B to design the structures.
Explanation: The master builder designs structures.
I unfortunately don't know much about architect scales. I tried to do research online, but I found no distinction between any of these scales. My best guess would either be a half or standard scale.
Everything you need to make a good meaningful sentence (and grammatically correct, of course), is to follow common rules. Do not forget to provide your sentence with complexity, but you don't have to make them too complicated, I mean you need to use key words, they will make your thought completed. And the second point is that you need to properly organize the sentence using correct word order. ion: