Proper amount of entrained air in concrete results in (i) Better workability (ii) Better resistance to freezing and thawing (iii) Lesser workability (iv) Less resistance to freezing and thawing A. (i) and (ii) B. (i) and (iv) C. (ii) and (iii) D. (iii) and (iv)

The correct answer is (i) and (ii).

Entrained air is tiny bubbles of air that are intentionally mixed into concrete during the mixing process. These bubbles help to improve the workability of concrete, making it easier to place and finish. They also help to improve the resistance of concrete to freezing and thawing, as the air bubbles act as tiny pockets that can absorb water without causing the concrete to crack.

Option (iii) is incorrect because entrained air actually improves the workability of concrete, making it easier to place and finish. Option (iv) is also incorrect because entrained air improves the resistance of concrete to freezing and thawing.