Who of the following scientists proved that the stars with mass less than 1.44 times the mass of the Sun end up as White Dwarfs when they die?

The correct answer is S. Chandrashekhar (option 2). Subrahmanyan Chandrasekhar derived the theoretical maximum mass that a white dwarf can have — now called the Chandrasekhar limit — beyond which electron degeneracy pressure cannot support the star against gravity. For typical white-dwarf compositions this limit is approximately 1.4 (often quoted as 1.44) times the mass of the Sun, so remnant cores below this mass end their lives as white dwarfs while more massive cores collapse further (to neutron stars or black holes). Chandrasekhar made and refined this calculation early in his career, and the limit is fundamental to white-dwarf stability and Type Ia supernova theory [1].

Sources

1. [1] http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/whdwar.html