The characteristic smell of garlic comes from a sulphur compound. Garlic contains a compound known as allicin, which is a sulfur-containing molecule. This gives garlic its distinctive smell and flavor.

Option 1 suggests that a chloro compound is responsible for the smell of garlic. This is incorrect because chloro compounds typically do not produce strong odours.

Option 3 suggests a fluorine compound. However, fluorine compounds are not responsible for the smell of garlic. Fluorine compounds are found in many different substances but do not produce characteristic garlic odor.

Option 4, acetic acid, is the main component of vinegar and not garlic. While acetic acid does have a strong odor, it`s not the smell we associate with garlic.

So, the correct answer is indeed option 2, a sulphur compound.