Answer:
The correct answer is letter "D": may sell some of your securities to repay the margin loan.
Explanation:
A Margin Call is issued when the equity in a margin account falls below a certain level. In the U.S. this level is set by the Federal Reserve (Fed) Board "Regulation T". Many brokers have their margin requirements known as "house requirements" usually with maintenance levels of 30 to 40%.
When a margin account falls below the margin limit and the trader ignores this, the broker can sell some of the securities of the trader to cover the margin losses.