Final answer:
The most likely reason why only Olivia's left arm fractured despite landing on both arms with the same force is that she may have instinctively protected her dominant right arm.
Step-by-step explanation:
The most likely reason why only Olivia's left arm fractured despite landing on both arms with the same force is that she may have instinctively protected her dominant right arm by not fully extending it or by using it to cushion the fall. This is a common reaction to protect the dominant arm from injury. By stretching out both arms, Olivia's left arm took the impact of the fall while her right arm was partially protected. As a result, the force applied to her left arm was greater, leading to the fracture.
Additionally, the bone structure and density of the left and right arms could also play a role. Bones may vary in thickness and density between individuals due to factors such as handedness or physical activity. It is possible that Olivia's left arm had a weaker bone structure than her right arm, making it more susceptible to fracture.