Q1: Centre of buoyancy is

ANS:B - centroid of the fluid displaced

The center of buoyancy is the centroid of the fluid displaced by the floating body. When an object is immersed in a fluid, it displaces a volume of fluid equal to its own volume. The center of buoyancy is the point at which the force of buoyancy, which is equal to the weight of the fluid displaced by the object, acts. It is essentially the center of mass of the displaced fluid volume. So, the correct option is: centroid of the fluid displaced.