(A)−(III),(B)−(I),(C)−(IV),(D)−(II)Caesium is used in devising photoelectric cells. Boron fibres are used in making bullet-proof vest. Silicones being surrounded by non-polar alkyl groups are water repelling in nature. Gallium is less toxic and has a very high boiling point, so it is used in high temperature thermometers.
| Column I (Element) | Column II (Uses) | ||
| i | Cs | c | Photoelectric cell |
| ii | Ga | a | High temperature thermometer |
| iii | B | d | Bullet-proof vest |
| iv | Si | b | Water repellent sprays |