Select the appropriate correction to the following sentence: you shouldn’t pat a strange dog, sometimes they’re not friendly.

The correct answer would be:

You shouldn't pat a strange dog; sometimes they're not friendly.

The semicolon or semi-colon is a punctuation mark used in the following three cases:

In lists that have internal commas, to make it easier to read. For example y favorite store is having a huge sale; you can buy pants, shirts, and shoes for half price.

Between two independent clauses, particularly with clauses that are complex,  have commas and don't have a coordinating conjunction. For example, You shouldn't pat a strange dog; sometimes they're not friendly.

When a comma replaces a full stop in a quotation. For example, "Is this your child?" he asked; "I found him outside".

they are most likely about to fight in the battle of gaul