You want a reply written in a friendlier, less formal style. What does OpenAI's prompting guidance suggest?

The principle — the things you want from an answer are usually easier to ask for than to engineer.

Why the key is correct — OpenAI's guidance is to use descriptive adjectives to indicate the tone, noting that words like formal, informal, friendly, professional, humorous or serious help guide the model, with the example of asking it to explain something in a friendly and engaging tone.

Why the others are wrong — repeating a request unchanged is chance rather than method. Tone is not fixed per model, so switching is a large lever for a small job. And an example helps but is not necessary, since the tone can simply be named.

Remember this — the same guidance says to be clear and specific and to refine iteratively. Name the tone, read the result, adjust.

Sources — OpenAI's prompt engineering best practices for ChatGPT.