The number we need in order to answer the question belongs in the space between the words "is" and "of". You left that blank blank, so there really isn't any question here to answer.
HOWEVER ... the refractive index of a medium can never be less than 1.0 , so we know for sure that <em>choice-a can't be</em> the correct answer.
Here if we assume that there is no air friction on both balls then we can say

now the acceleration is given as


so here both the balls will have same acceleration irrespective of size and mass
so we can say that to find out the time of fall of ball we can use


now from above equation we can say that time taken to hit the ground will be same for both balls and it is irrespective of its mass and size
Answer:
petroleum and Natural gas are fossil fuels
Explanation:
The answer is gravity. I hope this helps.
The answer is Monocline. And I checked it, it's correct.