In which of the following types of heat engines carburetor is used?

1. A

   Both diesel and petrol enginess

   Option (a) claims that a carburetor is used in both diesel and petrol engines. This is incorrect because diesel engines use fuel injectors instead of carburetors to introduce fuel into the combustion chamber.

2. B

   Steam engine

   Option (b) claims that a carburetor is used in a steam engine. This is incorrect because steam engines rely on external combustion of water to produce steam, entirely bypassing liquid fuel carburetion.

3. C

   Petrol engine

   Option (c) claims that a carburetor is used in a petrol engine. This is the correct option because petrol engines require a carburetor to mix air and fuel in the proper proportion before it enters the engine cylinders for spark ignition.

4. D

   Diesel engine

   Option (d) claims that a carburetor is used in a diesel engine. This is incorrect because diesel engines compress only air and inject diesel fuel directly at high pressure, making carburetors unnecessary.

Summary. Official key is (c) Petrol engine. A carburetor is a device that blends air and petrol for internal combustion engines. While petrol engines traditionally rely on this mixing device, diesel engines use fuel injection systems. Steam engines operate on an entirely different external combustion principle. Therefore, option (c) is the correct answer.