What is a margin call and when should we expect to receive one? a) When your broker calls you and askes you out to lunch. b) When a margin contract has ended and settled through a clearinghouse. c) When there is an unexpected rise in the price of a single security in an investors portfolio. d) When the value of an investor's margin account falls below the broker's required amount. The broker then demands that an investor deposit additional money or securities into the account so that it is brought up to the minimum value