An oxidising agent is a substance which can:
A.Accepts electrons
B.Donate electrons
C.Accept protons
D.Donate protons

Hint:Oxidising agent is a substance that has the ability to oxidise substances and itself get reduced. Potassium dichromate and potassium permanganate are strong oxidising agents that help in the oxidation of alcohols to carboxylic acids.
Complete step by step answer:
Oxidising agents are also known as oxidants that have the ability to get reduced in a chemical reaction and help in the oxidation of other substances. The oxidising agents are in their higher possible oxidation state and therefore get reduced. The reduction takes place due to gain of electrons.
Oxidation state helps in determining the degree of oxidation of an atom. Oxidation state are integers which can be negative, positive or zero.
Oxidising agents is a substance that has the ability to accept electrons. It accepts electrons that are transferred from another compound.
Therefore, the correct option is A..

Additional information
In a chemical reaction oxidation and reduction of atoms, molecules and ions takes place.
Oxidation is defined as the loss of electrons in a chemical reaction by an atom or ions. Oxidation takes place when the oxidation state of an atom, ion or molecule is increased.
Reduction is defined as the gain of electrons in a chemical reaction by an atom, molecules and ions. It takes place when the oxidation state of an ion, molecules and atom is decreased.

Note:
Substances that accept electrons are the oxidising agent ,they oxidise the other substances and themselves get reduced. When oxidation and reduction occur together , then it is known as redox reaction.
In oxidation, loss of electrons takes place whereas in reduction, gain of electrons takes place.