Problem: If the statement "All shirts in this store are on sale." is false, then which of the following statements must be true?
I. All shirts in this store are not on sale.
II. There is some shirt in this store not on sale.
III. No shirt in this store is on sale.
IV. Not all shirts in this store are on sale.
Answer Choices:
A. II only
B. IV only
C. I and III only
D. II and IV only
E. I, II and IV only
Solution:
II and IV are the only negations of the given statement.