Assertion (A) : Nichrome is used as a heating element in devices like electric toaster and electric geyser.

Reason (R) : Nichrome has high melting point and low resistivity.

The correct option is (A) is true and (R) is false.

Step 1: Analyze Assertion (A)
Nichrome is an alloy made primarily of nickel and chromium. It has a high resistivity and a high melting point, which allows it to produce a large amount of heat when an electric current passes through it without melting or oxidizing (burning) at high temperatures. Therefore, Nichrome is widely used as a heating element in electrical heating appliances such as electric toasters, irons, and electric geysers. Thus, Assertion (A) is true.

Step 2: Analyze Reason (R)
While Nichrome indeed has a high melting point, it has high resistivity, not low resistivity. High resistivity is essential for heating elements so that a significant amount of electrical energy is converted into heat energy according to Joule's law of heating:

$H=I^{2}Rt$

Because Reason (R) incorrectly states that Nichrome has "low resistivity", Reason (R) is false.

Conclusion:
Assertion (A) is true, but Reason (R) is false.