Answer to the question no- a

What I have learnt from the content :

Torsional rigidity, Breaking twist, Shear modulus.

Answer to the question no- b 

The twist for breaking of a yarn is called breaking twist. It also can be defined as the number of twists required to break a yarn. Breaking twist depends on the diameter of fiber and it is inversely proportional to its diameter.

That is, Tb ∞ 1/d

Where, Tb = Breaking twist,

d = diameter of fiber.