Answer to the question no-a

What I have learnt from this contents:

Definition of friction, importance & problem of friction, Minimization method of friction ,Amon tons Law & static capstan method, Math.

Answer to the question no-b

I want to learn more.

Answer to the question no-c

I understood all content of this topic after attending class.

Answer to the question no-d

Friction is important in textile industry. It is because, 

Friction holds the fiber in a sliver and hence material does not break due to self weight.

Friction helps in the drafting and drawing process.

Uniform tension can be maintained in winding and warping because of friction.

Friction helps in twisting during spinning.

Friction modifies the luster and appearance of a cloth

Friction makes more clean yarn.

So friction is important in the textile industry.