"What?" and "how?" questions are more open to discussion and feel less accusatory than "why?" questions.

Questions

Noun
People, places, or things.
Verb
An action word.
Adverb
A verb modifier.

Words

Harp ...on/upon
To dwell on persistently or tediously in speaking or writing.
To dwell on or recur to a subject tiresomely or monotonously.

He was always harping on the importance of taking vitamin supplements.

Phrases