Final answer:
By the Law of Syllogism, the valid conjecture is F: If a child can reach the red bar, then the child can ride the roller coaster, because reaching the red bar signifies the child is tall enough for the ride.
Step-by-step explanation:
Answering the student's question on which conjecture is valid by the Law of Syllogism given two premises:
- If a child is at least 4 feet tall, then he or she can ride the roller coaster.
- If a child can reach the red bar, then the child is at least 4 feet tall.
By the Law of Syllogism, which allows us to combine two conditional statements where the conclusion of one is the hypothesis of the other, we can make a valid conjecture. The resulting valid conjecture is:
F. If a child can reach the red bar, then the child can ride the roller coaster.
This is because reaching the red bar implies being at least 4 feet tall, which in turn implies that the child can ride the roller coaster.