Which of the following is not a guideline for choosing a research subject

Choose a subject you already know very well.

Explanation:

Choosing a subject that you already know very well is not a guideline for choosing a research subject. If you research a subject that you already know well, you will be more likely to have some bias or preconceived notions about the subject. Moreover, you will find the subject less interesting. Finally, this might diminish the impact of the research as you might not end up learning much.

its d because i know

it ends with a marriage, but also with prospero giving up his power.

the tempest is a play written by william shakespeare between 1610-1611, it narrates the story of prospero a magician that sets a storm to wreck a ship, this sets the story to kill the king of naples. while it is a romantic style play, it isn´t traditional because of the ending, it end with the marriage and the magician giving up his powers.