Final answer:
Bob and Mark's play where they interact, share toys, and create a story line is known as cooperative play. The answer is option A.
Step-by-step explanation:
The type of play where Bob and Mark are actively interacting with each other, sharing toys, and creating a storyline is called cooperative play.
Cooperative play occurs when children work together towards a common goal, such as building something or acting out a scenario. They share toys, take turns, and collaborate to achieve their objective.
For example, in the scenario of Bob and Mark playing astronauts, they are engaging in cooperative play by sharing toys like the spaceship and cooperating to create a storyline about landing on the moon.