Final answer:
Metals generally have positive oxidation numbers, especially transition metals which have variable oxidation states. These oxidation numbers often reflect the metals' tendency to lose electrons in chemical reactions, although some non-transition metals can also show variable oxidation states.
Step-by-step explanation:
Metals generally have positive oxidation numbers. This is reflective of the loss of electrons metals often undergo when forming compounds. For example, transition metals are a special case where they exhibit a variable oxidation state. This means that transition metals can have multiple positive oxidation numbers, as they tend to lose their 4s electrons before any of the 3d electrons.
Some transition metals can show a wide range of oxidation states; for instance, Manganese can have positive 2, 3, 4, 6, and 7 oxidation states. Furthermore, other non-transition metals like lead and tin also demonstrate variable oxidation states to a lesser extent. However, typically the oxidation number assigned to a metal in a molecule or ion is positive, which denotes a partial loss of electrons.
Therefore, while metals can exhibit both positive and negative oxidation numbers, they usually have positive ones. The correct answer to the question is:
A) Positive.