Distinguish between refraction and diffraction

Refraction is the change in direction of waves that occurs when waves travel from one medium to another. It is always accompanied by a wavelength and speed of change. Diffraction is the bending of waves around obstacles and openings.

i think the answer is a, hope this is right, that would be my best guess.

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.