When elements overlap, they are ordered on the z-axis (i.e., which element covers another). The z-index property can be used to specify the z-order of overlapping elements. Which set of statements about the z-index property are true?

Larger z-index values appear on top of elements with a lower z-index value. Negative and positive numbers can be used. z-index can only be used on positioned elements.
Smaller z-index values appear on top of elements with a larger z-index value. Negative and positive numbers can be used. z-index must also be used with positioned elements.
Larger z-index values appear on top of elements with a lower z-index value. Only positive numbers can be used. z-index must also be used with positioned elements.
Smaller z-index values appear on top of elements with a larger z-index value. Negative and positive numbers can be used. z-index can be used with or without positioned elements.