a) The poles of the magnet. The magnetic fields are closely packed at the poles of the magnet. The middle of the magnets are weaker and this might not test the true strength of the magnet

b) B. The magnet is able to attract the most paper clips compared to Magnet A and C.

c) No.



But if you want to be a smart-thing,
c) It depends on the geometry of the size and what you want the magnetic field to be doing. For example - if you want maximum holding power by direct contact with iron surface then surface area is important as well as magnet thickness but magnet thickness works as a diminishing parameter. When you have a 1 inch square magnet that is 2mm thick and you double it to 4 mm thick you will get about a 70-80% increase in force. However if you have a 1 inch cube and double it you may only see a 10-20% increase in holding power. The mass of magnet doubled but you did not see anywhere near that much of an increase in power if you stack them. If you place them side by side you will actually double your holding force because you have twice as much surface area.