An unstable nucleus loses the most mass if the nucleus emits
(1) an alpha particle (3) a positron
(2) a beta particle (4) a gamma ray

Answer is (A) - an alpha particle.

Alpha particle is a ₂⁴He nucleus. When a parent atom emits an alpha particle, the atomic number reduces by 2 in the formed daughter atom while reducing the mass number by 4. Hence, emitting of alpha particles loses the most mass from the unstable nucleus.

Mass of positron and the mass of an electron are same as 9.109 x 10⁻³¹ kg. Those masses are relatively very low. . Emitting of gamma ray means the releasing of energy from the unstable nucleus. Hence, gamma rays do not have masses.

i dont know the answe