Assertion: The core concern of geography as a discipline is to understand the earth as home of human beings and to study all those elements which have sustained them.
Reasoning: The dichotomy between physical and human is not a very valid one because nature and human are inseparable elements and should be seen holistically.

Both Assertion (A) and reasoning (R) are correct and but R is not the correct explanation of A.

The correct answer is option 2: Both Assertion (A) and reasoning (R) are correct and but R is not the correct explanation of A.

Assertion: The core concern of geography as a discipline is to understand the earth as home of human beings and to study all those elements which have sustained them. This is correct because geography indeed focuses on studying the Earth's surface and how human activities interact with it.
Reasoning: The dichotomy between physical and human is not a very valid one because nature and human are inseparable elements and should be seen holistically. This is also correct because geography as a discipline often emphasizes the interconnectedness of human and physical processes on the Earth's surface.

R Does not Explain A: The Reasoning provides additional context about the inseparability of nature and human elements in geography, but it doesn't directly explain why the core concern of geography is to understand the earth as the home of human beings and study elements that sustain them.