Blister copper is a term commonly used in the field of metallurgy. It refers to a particular form of copper that contains impurities. Let's analyze each option to understand why all of them are correct:

a) Pure copper: Blister copper is not pure copper. It is an intermediate product obtained during the process of refining copper. It contains impurities, which are removed in subsequent steps to obtain pure copper.

b) An ore of copper: Blister copper is not an ore of copper. Ores are naturally occurring rocks or minerals from which valuable substances like metals can be extracted. Blister copper is a product obtained from the smelting of copper ores.

c) An alloy of copper: Blister copper is not an alloy of copper. Alloys are formed by mixing two or more metals or a metal with non-metallic elements. Blister copper is not intentionally alloyed with other elements; rather, it is a result of the smelting process that leaves impurities in the copper.

d) Copper containing 2% impurities: This statement is incorrect. Blister copper usually contains a higher percentage of impurities, typically around 2-3%. The impurities can include elements like sulfur, iron, arsenic, and others. These impurities are undesirable in the final product, and the blister copper needs further refining to remove them.

In summary, all the options A, B, and C are correct statements about blister copper. It is not pure copper, it is not an ore of copper, and it is not an alloy of copper. Blister copper is an intermediate product in the process of refining copper, and it contains impurities that need to be removed to obtain pure copper.