If I receive a margin call, it is because ... a. I have a long position, the price has risen, and the broker wishes to loan me more money. b. I have entered a long position on a stock of marginal value. c. I have entered a short position on a stock which the broker deems to be of marginal value. d. I have exited a long or short position without remembering to pay back the loan to the broker. e. I have a long position, the price of the stock has dropped, and I need to post cash or liquidate