Questions

The water rise in a capillary tube dipped in water is such that the weight of water in the tube above the surface of water in the vessel is equal to (balances) the upward force due to surface tension. So it is clear that if the the bore (radius) to the tube is decreased, the height of the water column in it must be greater.  So, (a) is correct.

Ecology is the branch of science which deals with the study of Ecosystem (relation between the Organisms and their Environment.)

The perfect paging size varies from system to system, so there is no single best when it reaches to page size. There are several factors to consider in order to come up with a fitting page size, such as paging time, page table, and its effect on the total performance of the operating system.