Step 1: Fact-checking the Assertion.
Rural development is a holistic term. While farming is the backbone, the concept also includes social infrastructure like sanitation, literacy, land reforms, and the development of non-farm employment. Thus, (A) is true.
Step 2: Fact-checking the Reason.
Since a vast majority of the rural workforce still relies on farming for their livelihood, the state must intervene to ensure food security and income stability. Thus, (R) is true.
Step 3: Linking (A) and (R).
Because agriculture is the main source of sustenance (as stated in R), any plan for rural development must prioritize agricultural stability while also expanding into other areas to ensure total upliftment. The reason provides the justification for why agricultural focus is the starting point of the broader developmental goal.
Final Answer: Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A).