The correct answer is: A. Active
Busy means being occupied with many things. It is often used to describe someone who is working hard or who has a lot of things to do.
Active means being physically or mentally engaged in an activity. It can also mean being lively and energetic.
Occupied means having one’s attention or time taken up by something. It can also mean being in possession of something.
Preoccupied means having one’s mind filled with thoughts about something else. It can also mean being concerned or worried about something.
Diligent means being careful and hardworking. It can also mean being attentive to detail.
In this case, the word “busy” is most closely related to the word “active.” Both words describe someone who is engaged in an activity. However, “busy” can also be used to describe someone who is occupied with many things, while “active” is more specifically used to describe someone who is physically or mentally engaged in an activity.