Which of the following describes an element that is oxidized in a reaction a it gains electrons during a reaction b it has a decrease in it oxidation number c al yields al3+ + 3e- d f2 + 2e- yields 2 f-

Answer : The correct option is, (C)

Explanation :

Redox reaction occurs when the electrons are lost by an atom of one reactant and gained by an atom of another reactant. There are two process involved in the redox reaction.

Oxidation : It is a process in which the element lose an electron during a chemical reaction. An element that is oxidized in a reaction has a increased in  it oxidation number.

Reduction : It is a process in which the element gain an electron during a chemical reaction. An element that is reduced in a reaction has a decreased in it oxidation number.

From this we conclude that

The option A and B are incorrect as per definition of the oxidation.

The option D is also incorrect because in this the oxidation number of fluorine decreases from (0) to (-2). So, this is a reduction process.

The option C is correct because in this the oxidation number of aluminium increases from (0) to (+3). So, this is a oxidation process.

Hence, the correct option is, (C).

a:

by the combination of an unlimited number of elements

it is b that is the answer.