Answer is D. remain at $30,000.
Explanation:
Rick's Internet Corporation balance in retained earnings = $30,000
Appropriated earning for future business expansion = $15,000
This appropriated earning set for future use will have no effect on the total retained earnings, because for appropriate retained earnings, the entry is to debit the retained earnings account.
Also, it would be board's decision if they want to use the money from the retained earnings or add more capital to it.