Explanation:

- The correct word for blank no. 3 should reflect the act of clearing or destroying the fields by removing the rice chaff.

- Option 1: "racing" refers to moving quickly, which doesn't fit the context.

- Option 2: "raising" means to lift or elevate something, which isn't relevant here.

- Option 3: "rising" means to go upward or elevate in position, which doesn't describe the action in the passage.

- Option 4: "razing" means to completely destroy or flatten, which accurately describes the act of clearing fields off rice chaff by burning.

The correct answer is Option 4: "razing."