Explanation:

- The leftmost group of the periodic table is Group 1, known as the alkali metals.

- Alkali metals are classified as base metals. They include elements such as lithium, sodium, and potassium.

- Noble gases are located in Group 18, far right of the periodic table.

- Halogens are located in Group 17, just to the left of the noble gases.

- Non-metals are found in various groups, but not predominantly in Group 1 or the leftmost part.

Option 4: Base metals is included in the leftmost group of the periodic table.