Answer:
a.They have a smaller proportion of heavy elements.
Explanation:
As a star grows old , its metal content becomes low . Our sun is Population I star which means it is very new . Its metal content is 1.4 % . By the term metal we mean any element heavier than helium . Population II stars are older than population I stars . They will have lesser content of metal . Population III are oldest star group which have metal content as less as .015 % .
The answer is constant acceleration.
<h3>Hi there !</h3><h2>Option A is correct </h2>
<h3> Please refer the attachment for explanation</h3><h2>Stay safe, stay healthy and blessed</h2><h2>Have a marvelous day</h2><h2>Thank you</h2>
During the collision between two balls on the pool table there is no external force along the line of collision between them
Since there is no external force on it so here we can say

here we have

so we can say

since there is no external force so we can say during the collision the momentum of two balls will remain conserved