### Your answer to (2.2):ACD 2.3 Imagine you initially observe the sell portion of an order book as follows Sell Price Size ID 20 1000 1 21 500 2 22 800 3 23 1200 4 An investor placed a buy order. Immediately after the order execution (assume no other orders have been submitted/executed), the same sell portion of the order book becomes Sell Price Size ID 21 500 2 22 800 3 23 1200 4 What kind(s) of order has this investor possibly submitted? A. A market order. B. A limit order. C. A market-to-limit order. D. A market-with-protection order