What are the answer choices, if there are any?
The planets have (their) moons. So the answer would be planets.
Answer: F = ma,
Explanation:
the most famous equation in physics, establishing an equivalence between energy and mass. But is this the most important equation in physics? Knowledgeable scientists will tell you no. The most important equation in physics is F = ma, also known as Newton's second law of mechanics.
Answer:
Momentum, 
Explanation:
The wave function of a particle is given by :
...............(1)
Where
x is the distance travelled
t is the time taken
k is the propagation constant
is the angular frequency
The relation between the momentum and wavelength is given by :
............(2)
From equation (1),


Use above equation in equation (2) as :

Since, 

So, the x-component of the momentum of the particle is
. Hence, this is the required solution.