In which numbered cells should he place pressure? 2, 4, and 5 1, 4, and 6 2, 3, and 5 1, 3, and 6

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

the order for strong to weak forces such as

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force

the fundamental forces are those forces that act between to objects or element to make interactions. there are four types of fundamental forces such as strong and weak nuclear forces (due to protons and electrons), electromagnetic force (due to the motion of electrons) and gravitational force (due to orbital movement of the planet). if these forces are arranged on the basis of their maximum strength then the order is

strong nuclear force → electromegnetic force → weak nuclear force → gravitational force