Doubt

2 is incorrect because , newtons 3rd law states that every action has equal and opposite reaction. So wt of body equals to normal reaction

It was option 3, not 2 mistypd

Here multiple options are correct i.e 3rd and 4th Reason is Newton's third law is: For every action, there is an equal and opposite reaction. The statement means that in every interaction, there is a pair of forces acting on the two interacting objects. The size of the forces on the first object equals the size of the force on the second object

Weight, W=mg=5×10=50N

Hence, The normal force on the block equals its weight because of Newton's third law equal to 50 N

Option 3 is incorrect