Electronic Devices and Circuits - Engineering

Q1:

Assertion (A): Alkali metals are used as emitters in phototubes. Reason (R): Alkali metals have low work functions.

A Both A and R are true and R is correct explanation of A

B Both A and R are true but R is not a correct explanation of A

C A is true but R is false

D A is false but R is true

ANS:A - Both A and R are true and R is correct explanation of A

Please explain it.