Answer:
If Alpha Investment Advisers' assets under management have fallen below the $100 million threshold for SEC registration, they would need to take action to withdraw from SEC registration. The correct answer is C) Withdraw from SEC registration within 180 days of the adviser's fiscal year-end.
Under the Investment Advisers Act of 1940, advisers with less than $100 million in assets under management are generally required to register with the state(s) in which they conduct business, rather than with the SEC. In this case, since Alpha's assets under management have fallen to $75 million, they are no longer eligible for SEC registration and must withdraw their registration. The adviser has 180 days from the end of their fiscal year to do so