Which is an example of a mixture

A mixture is two or more substances that have been combined together but each substance is not changed chemically.

Examples of mixtures include:

1. Sea water. This is a mixture of water and various salts.

2. Gunpowder. This is a mixture of potassium nitrate, suilfur and carbon

3. Crude oil. This is a mixture of organic compounds, mainly hydrocarbons.

4. Ink. This is a mixture of colored dyes which can be separated using  chromatography.

5. Dry air. Air is a mixture of nitrogen,oxygen, argon, carbon dioxide, neon and tiny traces of other gases.

what grade is this in??