The correct statement regarding defects in a crystalline solid is:

Silicon gives p-type of semiconductor on doping with:

1. Germanium.

2. Arsenic.

3. Selenium.

4. Boron.

The appearance of colour in solid alkali metal halides is generally due to:

1. F-centres.

2. Schottky defect.

3. Frenkel defect.

4. Interstitial positions.