Answer:3.49 m/s
Explanation:
Given
Speed of marble at Bottom 
Diameter of loop 
As Energy is conserved therefore Energy at top is equal to energy at bottom

,where
is the velocity at bottom







D. Nucleus because it is not a part of the group.
This question is wrong because in momontum we will write acceleration instead of speed. suppose acceleration is 5m/s2 then
P= ma
then put values