Answer:
a.when a corporation owns more than 50% of the common stock of another company
Explanation:
Many a times, a parent company holds stock in it's own subsidiary company. Consolidation refers to presentation of combined profitability of a group wherein a Parent Co holds majority of the common stock i.e more than 50% of the common stock in it's subsidiary.
Such a presentation presents the combined picture of a group and helps in better comprehension and understanding by the users of the financial statements.
If a parent owns 100% stock in it's subsidiary, such subsidiary is referred to as a wholly owned subsidiary.