Given below are two statements.

Statement I : Frenkel defects are vacancy as well as interstitial defects.

Statement II : Frenkel defect leads to colour in ionic solids due to presence of F-centres.

Choose the most appropriate answer for the statements from the options given below :

Select the correct statements

(A) Crystalline solids have long range order.

(B) Crystalline solids are isotropic

(C) Amorphous solid are sometimes called pseudo solids.

(D) Amorphous solids soften over a range of temperatures.

(E) Amorphous solids have a definite heat of fusion.

Choose the most appropriate answer from the options given below.

The parameters of the unit cell of a substance are a = 2.5, b = 3.0, c = 4.0, $$\alpha$$ = 90$$^\circ$$, $$\beta$$ = 120$$^\circ$$, $$\gamma$$ = 90$$^\circ$$. The crystal system of the substance is :

Given below are two statements. One is labelled as Assertion A nd the other is labelled as Reason R.

Assertion A : Sharp glass edge becomes smooth on heating it upto its melting point.

Reason R : The viscosity of glass decreases on melting.

Choose the most appropriate answer from the options given below.