Final answer:
The false statement about decision trees is that the expected payoff must always equal zero. Expected payoffs are calculated by summing the products of payoffs and their probabilities, and can be different from zero.
Step-by-step explanation:
All of the following statements about decision trees are true EXCEPT: A. The expected payoff must always equal zero. This statement is not true; the expected payoff is the sum of the possible payoffs, each multiplied by their respective probabilities, and does not necessarily equal zero. B. Square nodes represent decision points. This statement is true; square nodes are typically used in decision trees to indicate points where a decision-maker has a choice. C. Payoffs are often expressed as the present value. This statement is also true; it is common practice in decision analysis to express payoffs in terms of present value, which accounts for the time value of money.