Option 1 suggests that both the assertion and the reason are true and the reason correctly explains the assertion. However, although the eastern coast of India does produce more rice due to more fertile soil and a larger agricultural sector, the amount of rainfall is not the primary reason for this.

Option 2 also acknowledges that both statements are true, but it correctly identifies that the reason given does not correctly explain the assertion.

Option 3 suggests that the assertion is correct but the reason is false. This is the correct answer as the eastern coast of India does produce more rice, but it`s not because it receives more rainfall.

The last option, Option 4, indicates that only the reason is true and the assertion is false. This is incorrect, as the eastern coast does indeed produce more rice. Therefore, the answer "3" is correct.