Questions

The weight of the man mg is acting on the floor. As the lift is moving up with an acceleration, say a, the man too in it is having this acceleration. The force producing this acceleration is ma. By Newton's third law, this force will have an equal reaction pressing the floor equal to ma. Therefore the total resultant reaction on the floor is mg+ma = m(g+a) which is mg, the weight of the man. So (a) is correct.

The Doppler effect or Doppler shift is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. 

A restrictive clause is one that limits the meaning of the word it describes.

For example :: 

The girl who lives next door is beautiful.

This restrictive clause limits "the girl" to say it's specifically the one next door.

Configuration management is not concerned with the choice of the hardware configuration for an application.

Configuration management is concerned with the development of procedures and standards for cost-effective managing and controlling charges in an evolving s/w system.

It includes

1)software versions maintenance

2)controlling changes in documentation

3)controlling changes to the source code

4) management activities