Mexico is not exempt from earthquakes nor are they always mild.

which answer shows proper comma usage?

mexico is not exempt from earthquakes, nor are they always mild.
mexico is not exempt, from earthquakes nor are they always mild.
mexico, is not exempt from earthquakes, nor are they always mild.
mexico is not exempt from earthquakes, nor, are they always mild.

The answer which shows proper comma usage is the following one:

Mexico is not exempt from earthquakes, nor are they always mild.

Explanation:

Commas are often used to separate different clauses, and that is what happens in the sentence above. Check it out:

Mexico is not exempt from earthquakes, nor are they always mild.

                                  ↓                                                     ↓

                             Clause 1                                          Clause 2

Both clauses can be called so because both have their own subject and predicate, and both express a complete thought. Therefore, they must be separated by a comma.

thats harsh

explanation:

i’m pretty sure it is the second