Match the points under List I with those under List II.

List I (Instrument)	List II (Use)
1. Sextant	a. Measures the angle between two visible objects
2. Udometer	b. Measures small quantities of radiant heat
3. Thermopile	c. Measures the temperature of a surface
4. Pyrometer	d. Measures the amount of rainfall

Correct option is B

The correct answer is (b) 1-a, 2-d, 3-b, 4-c.
Here is the correct matching of the instruments with their uses:
· Sextant - (a)Measures the angle between two visible objects: A sextant is a navigational instrument used to measure the angle between two visible objects, commonly used in celestial navigation to determine the angle between a celestial body and the horizon.
· Udometer - (d) Measures the amount of rainfall: Also known as a rain gauge, an udometer is an instrument used to measure the amount of liquid precipitation over a set period.
· Thermopile - (b) Measures small quantities of radiant heat: A thermopile is an electronic device that converts thermal energy into electrical energy, typically used to measure small amounts of radiant heat.
· Pyrometer - (c) Measures the temperature of a surface: A pyrometer is a type of thermometer used to measure high temperatures from a distance, particularly the temperature of a surface.