Question No. 17 to 20 consists of two statements, Assertion and Reason. Answer these questions selecting the appropriate option given below. a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion. c) Assertion is true, but Reason is false. d) Assertion is false, but Reason is true.


17. Assertion: The combustion of fossil fuels leads to global warming.
Reason: Coal and petroleum are fossil fuels.

18. Assertion: In agriculture microorganisms are used to increase soil fertility by fixing nitrogen.
Reason: Blue green algae and Rhizobium bacteria convert atmospheric nitrogen into nitrogenous compounds.

19. Assertion: Roughening of a surface helps to increase the friction.
Reason: Liquids and gases do not exert any friction.

20. Assertion: Growth hormone is produced by pituitary gland.
Reason: Prolonged deficiency of iodine in diet causes a disease called goitre.​