Newton is SI unit of . . . . . . . .?

Answer: Option B

Let's break down the options:
Option A: Weight and Velocity - Velocity is measured in meters per second (m/s), not Newtons.
Option B: Weight and Force - This is the correct answer.
Option C: Weight and Mass - Mass is measured in kilograms (kg), not Newtons.
Option D: Weight and Acceleration - Acceleration is measured in meters per second squared (m/s²), not Newtons.

Newton's Second Law of Motion states that Force (F) = Mass (m) x Acceleration (a). The unit of force derived from this equation is the Newton.
Weight is a type of force, specifically the force of gravity acting on an object's mass. Therefore, weight is also measured in Newtons.

Therefore, the correct answer is B: Weight and Force.