An extinct volcano does not erupt or/and is unlikely to do so even in future.

[Tan Elaine]

An extinct volcano does not erupt or/and is unlikely to do so even in future.

The teacher answer is 'and', but I think it should be 'or' because of 'does not erupt', which is negative. Am I correct?

Thanks.

[Bennevis]

"is" is correct. Try breaking the sentence into two parts.

An extinct volcano does not erupt or/and is unlikely to do so even in future.

An extinct volcano does not erupt.
An extinct volcano is unlikely to do so even in future.

We combine them using "and".

If you want to use "or", you have to say:
An extinct volcano does not erupt; nor is it likely to do so even in future.

[SoothingDave]

The two ideas go hand-in-hand, so they are joined by "and." The reason we say it is unlikely to erupt again is because it has not erupted for a long time.

No one would ever say "it erupted last week, but it is unlikely to do so again."

[Bennevis]

An extinct volcano does not erupt or/and is unlikely to do so even in future.

You can also say:
An extinct volcano does not erupt and is unlikely to do so either even in future.