Detailed Explanation:

Rajasthan's low rainfall is primarily due to the Aravalli Range's orientation—it runs parallel to the Arabian Sea monsoon winds, preventing orographic uplift.

The Bay of Bengal branch loses most moisture over the Gangetic plains before reaching Rajasthan. Without a perpendicular mountain barrier to force air upward, winds remain at low altitude and do not cool sufficiently to condense into rainfall.

Therefore, the absence of barriers to cause necessary uplift makes Option 3 the correct answer.