Select the most appropriate option to fill in blank number 4.
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. challenge.
The word challenge is often used to describe something that is difficult yet interesting or worthwhile.
In this case, the idea is that organic farming might require more effort, but it's still seen as a rewarding challenge.
The other options, like obstacle or burden, suggest something negative, while the proposition doesn’t quite fit the context of difficulty or effort.