not only but also, position of also

[sitifan]

1. Not only is smoking dangerous to a smoker, but it can also harm the people around him.
2. Not only is smoking dangerous to a smoker, but it also can harm the people around him.
3. Not only is smoking dangerous to a smoker, but also it can harm the people around him.
Which of the above sentences do you think is the best?

[Clark]

Number 1 is correct, the others are doubtful.

[philadelphia]

I would say the third one in first: Not only is smoking dangerous to a smoker, but also it can harm the people around him.

Though, the first one is also correct but a bit far from the first usage of not only... but also.

Not a teacher at all

[Soup]

As with other correlative conjunctions, you should follow each part of the not only … but also … construction with an element of the same grammatical type. Thus, instead of She not only bought a new car but also a new lawnmower, you should write She bought not only a new car but also a new lawnmower, because in this version both not only and but also are followed by noun phrases

Source § 5. not only … but also. 2. Style. The American Heritage Book of English Usage. 1996

not only is smoking dangerous to a smoker <not only + verb>
but it also can harm the people around him <also + verb>
but it can also harm the people around him <also + verb>

[albertino]

1. Not only is smoking dangerous to a smoker, but it can also harm the people around him.
2. Not only is smoking dangerous to a smoker, but it also can harm the people around him.
3. Not only is smoking dangerous to a smoker, but also it can harm the people around him.
Which of the above sentences do you think is the best?

Hi, sitifan. For easy understanding, you'd better change the inverted order of the sentence back to its normal order first. So,
"Smoking not only is dangerous to a smoker, but (it can) also harm the people around him.
Parellel structure
Not only (noun) but also (noun)
Not only (verb) but also (verb)
Not only (gerund) but also (gerund)

After building up your confidence in their usage, you can use the inversion order correctly.
(Not a teacher)

[sitifan]

not only ... but also

[RonBee]

Sitifan, follow Soup's advice and use either the first or the second sentence.