Could you please help me with this?

The importance of experimental learning depends strongly on the nature of the activity: there are high-risk activities in which the agents have to limit their experiments because they could conflict with the “normal performance” that has to be achieved. Airline pilots or surgeons cannot learn in this way. Similarly, people managing a marshalling yard or regulating the flow of subway train traffic will avoid any type of experiment in the normal course of their work. By contrast, a teacher can carry out educational experiments and a craftsman can look for new solutions to a particular problem during the production process. The error element of their professional trial-and-error is rarely consequential at least insofar as outcomes can be rapidly assessed and methods adapted. The fact of being able to carry out this type of learning depends on the nature of the risk and the (A) immediacy (or (B) delay) of the effect. Thus, (C) explicitly cognitive learning consists of a series of planned but (D) weakly controlled experiments.

Which one is linked to high-risk activities, (A) or (B)?

Is (C) a high-risk activity or "a low-risk activity"?

What does (D) mean? Are they 'limited experiments' or "not so limited experiments"?

Thank you so much.