In both sentences, the preposition "on" is optional, and either version is correct. Here’s a quick comparison of how they sound: 1. With "on": * Adds a bit more emphasis on the action and can sound slightly more conversational. * "She was puffing on a cigarette at the time." * "I sat puffing on my cigar." 2. Without "on": * Sounds slightly more direct and is often used in more formal writing. * "She was puffing a cigarette at the time." * "I sat puffing my cigar." Both are natural, so it really comes down to preference. The meaning remains the same either way!

The preposition "on" is optional in both sentences, but using it slightly changes the tone. Here’s how each option works: With "on": "She was puffing on a cigarette at the time." "I sat puffing on my cigar." Using "on" gives a bit more focus to the ongoing action and can add a casual, conversational feel. It’s common in informal English and is slightly more descriptive, emphasizing the act of smoking. Without "on": "She was puffing a cigarette at the time." "I sat puffing my cigar." Without "on," the sentences are still correct, but the phrasing sounds a bit more concise or formal. This version focuses more directly on the action without the additional emphasis on the process. Both versions are grammatically correct, so it’s really a matter of personal preference and tone. For a more conversational feel, use "on"; for a more straightforward style, you can omit it.

without "on" sounds more colloquial.

Both are technically acceptable, but I would say WITH 'on' is better in both cases.

Definitely with. You could also use 'puffing at' or 'puffing away at/on'. Including 'away' gives the impression of someone performing a continuous behaviour in a very absorbed or enthusiastic manner.