Which statements below correctly describes the process of reduction in a redox reaction. Choose the 2 correct statements.



a
Occurs when the oxidation number of an element decreases in chemical reaction.
b
Occurs when the oxidation number of an element increases in chemical reaction.
c
Occurs when atoms lose electrons during bonding.
d
Occurs when atoms gain electrons during bonding.

The correct statements are:

a) Occurs when the oxidation number of an element decreases in a chemical reaction.
d) Occurs when atoms gain electrons during bonding.