In this passage, what do you understand by this context, "Flow puts the process of active engagement center-stage, along with a blurring of the boundary between self and activity".

• A. Gardening makes people forget all and everything.
• B. Gardening tempts people to see what might happen next.
• C. Flow is highly focused mental state.
• D. The flow of 'gardening' as an activity is intriguing.