Fusion processes, like combining two deuterons to form a He nucleus are impossible at ordinary temperatures and pressure. The reasons for this can be traced to the fact: (a) nuclear forces have short-range (b) nuclei are positively charged (c) the original nuclei must be completely ionized before fusion can take place (d) the original nuclei must first break up before combining with each other
Correct options are A) and B) Two deuteron can combine to form He atom when their nuclei come close to nuclear range where electrostatic repulsive force between positively charged deuterons does not act. The electrostatic force increases very high on decreasing their distance. (∵F∝r21) To overcome this electrostatic repulsive force nuclei need very high temperature and pressure. Hence to combine two nuclei, they must reach closer of the range of where nuclear force acts and electrostatic repulsive force does not act
