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

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

c

Occurs when the oxidation number of an element increases in chemical reaction.

d
Occurs when atoms lose electrons during bonding.