Answer:
The answer is A and C.
Explanation:
Only two factors are relevant when dealing with the gravitational force between two objects - their mass and their distance apart from one another. Gravity's force is proportional to the product of the masses of the two objects and is inversely proportional to the square of the distance between them.
Answer:
emf will also be 10 times less as compared to when it has fallen 
Explanation:
We know, from faraday's law-

and 
So, as the height increases the velocity with which it will cross the ring will also increase. 
Given


Now, from 

From equation a and b we see that velocity when dropped from
is 10 times greater when height is 40
so, emf will also be 10 times less as compared to when it has fallen 
The correct answer would be the last one
6.35x10^-4 OR 6.3x10-4 (if only one decimal number is allowed)