発達　and 発展
I know that they both mean ''to develop''. But i came across this sentence:
’’　人間はほかの動物より脳が（a. 発展 b. 発達）してる。
The correct answer is b. Why　発展　 is no correct? Do they work differently?

Question

発達　and 発展
I know that they both mean ''to develop''. But i came across this sentence:
’’　人間は ほかの 動物より脳が（a. 発展 b. 発達）してる。
The correct answer is b. Why　発展　 is no correct? Do they work differently?

Answer

"発達" means getting closer to a more completed state as it grows. We use "発達" about the functions and natural phenomena of living organisms and organs, such as ’発達 of mind and body", "発達したdogs of olfaction" and "developed low pressure". 
 "発展" will expand as the momentum and power of things increases.
is this enough for you?

Answer

発達：生物や身体の機能が成長すること。
発展：物事の勢いが増し広がっていくこと。

Both in English, development and they are close meanings. Bat. We use '発達' for living things and the body.

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