Final answer:
Option C correctly deduces from the original statement that Maria's favorite joke is independent of the river overflowing, which is a logical implication without suggesting causation.
Step-by-step explanation:
The statement provided, "If the river is overflowing, then that is Maria's favorite joke," is a conditional statement implying that Maria's favorite joke being told depends on the occurrence of the river overflowing. From the given options, the only statement that can be deduced logically from the original statement is C. Maria's favorite joke is unrelated to whether the river is overflowing. This is because the original statement does not imply causation or any functional relationship between the river overflowing and the joke; it only sets a condition under which the joke is Maria's favorite. Options A, B, and D are incorrect because they imply causation, don't follow from the original statement, or make an assumption about the humorous value of the joke that was not present in the original statement.