Assertion (A): The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil and thus create fertile soil.

Reason (R): Agricultural fields are covered with layers of volcanic ash and dust making them unsuitable for cultivation.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R does not explain A.
3. A is true but R is false.
4. A is false but R is true.

Both A and R are true and R is the correct explanation of A.

Explanation — Agricultural fields are covered with layers of volcanic ash and dust making them unsuitable for cultivation, but only temporarily. In fact, once weathered and broken down the lava and ash deposited during an eruption provides valuable nutrients to the soil making it fertile.