When ice melts, then the

The correct answer is (a). When ice melts, it expands and its volume increases. This is because the molecules in ice are arranged in a crystal structure that takes up more space than the molecules in liquid water. When the ice melts, the molecules are able to move around more freely and take up less space, resulting in an increase in volume.

Option (b) is incorrect because the volume of ice increases when it melts. Option (c) is incorrect because the mass of ice does not change when it melts. Option (d) is incorrect because the mass of ice does not decrease when it melts.