Answer: The correct option is 3.
Explanation: Radioisotopes that emit alpha-particles are termed alpha-emitters. These isotopes undergo alpha-decay.
Those radioisotopes that emit beta-particles are called beta-emitters. They undergo beta-minus decay, in which a neutron converts to a proton and an electron.
Isotopes that emit positrons are known as positron-emitters, undergoing beta-plus decay where a proton becomes a neutron.
From the options given,
Option 1: All three isotopes undergo beta-minus decay.
Option 2: Cs-137 and Tc-99 undergo beta-minus decay.
Fr-220 undergoes alpha-decay.
Option 3: Kr-85 undergoes beta-minus decay.
Ne-19 undergoes positron decay.
Rn-222 undergoes alpha decay.
Option 4: All three isotopes undergo beta-minus decay processes.
Therefore, the correct choice is 3.
