When two plants, A and B, were planted together in a field outdoors, plant A produced vegetables, and plant B produced flowers which attracted pollinators. It was noted that when they were grown apart from each other, plant A did not produce vegetables, but plant B still produced flowers. Which of the following is the MOST likely reason plant A did not produce vegetables when planted away from plant B?

The most likely reason plant A did not produce vegetables when planted away from plant B is that the insects that pollinated plant B also pollinated plant A.
Vegetables are typically the result of successful pollination, either by wind or by pollinators like insects. In this case, when plant A and plant B were planted together, the flowers of plant B attracted pollinators, which likely facilitated the pollination of plant A as well. As a result, plant A produced vegetables.
When the plants were grown apart from each other, plant A did not have access to the same pollinators that were attracted to plant B's flowers. Consequently, plant A did not receive sufficient pollination, leading to a lack of vegetable production.