Question

Protostar is a developing star not yet hot enough to engage in the process of
A. Nuclear fusion
B. Nuclear fission
C. Atomic transmission
D. Atomic emission

Answer 1

Hint: The developing stage of a star is known as the protostar. Nuclear fusion reaction takes place only at high temperatures. The protostar will continue to collapse under gravity until it gets hot enough so that nuclear fusion will take place to counteract gravitational pull.

Complete step by step answer:
A star in its developing stage is known as a protostar. A star is formed when a cloud of gases contracts themselves under gravity. It will continue to collapse until the hydrogen fusion starts to take place at a high temperature which prevents the collapse. We know that the fusion reaction takes place only at a very high temperature. In the fusion reaction, two small nuclei combine together to form a large nucleus. A high temperature is required to provide the necessary energy for the nucleus to combine. This is because when the nuclei combine there will be Coulomb repulsion between the nuclei. Since like charges repel each other. So, enough energy in the form of heat energy is necessary to overcome this Coulomb repulsion and fusion to take place.
So, in the developing stage when it is called a protostar there is not sufficient heat energy for the fusion reaction to occur.
Thus, a protostar will not engage in the process of nuclear fusion.
When it becomes hot enough then fusion starts and it becomes a main-sequence star.
A mainstream star is a star that can fuse hydrogen and which exists in a state of hydrostatic equilibrium, that is this fusion energy will oppose the force of gravity which is causing it to compress thereby reaching an equilibrium. So, protostars keep collapsing until they gain enough pressure to produce a high temperature which can promote fusion reaction.

Therefore, the correct answer is option A.

Note:
Remember that a protostar is not a different kind of star; it is the name given to the developing stage of stars. The star is in the collapsing stage in this phase until the pressure becomes high enough to produce high temperatures which promotes nuclear fusion. Then it becomes a regular star like our sun.