Answer:
C) Fair value, May 1, 2009.
Step-by-step explanation:
When a company acquires another company in stages (2, 3, 4 o even more), and the parent company is finally able to purchase more than 50% of the stocks, enough to carry out the business combination, it must adjust its carrying values.
Once the 50% threshold is passed, the parent company must adjust its previous investments to the fair value of the acquired company, just like any other acquisition.
Since Zooco reached 60% in May 1, 2009, then that is the date for the adjustment of the investment account. Similarly to any other acquisition, the difference between previous carrying value and fair market value results in a gain or loss.