The correct option is B Floatation
A boat should be able to float in the water. Even though boats are made of metals which have higher density than water, when we consider the size of the boat and it's volume as a whole, the density is less than that of water which allows it to float. Appearance, Transparency and Lustre are irrelevant properties that won't help the boat float on the water. Hence, the mateiral should have floatation property if it is required for making the boat