Which of the following metals can be cut with a knife?

The correct answer is option 2. Sodium.

Among the options provided, sodium is a metal that can be cut with a knife. Sodium is a soft metal that is relatively easy to cut with a knife. It has a low melting point and is highly reactive, often stored under oil to prevent reaction with moisture in the air. When freshly cut, sodium has a shiny surface but quickly tarnishes due to a reaction with oxygen and moisture in the air. So, the correct answer is Sodium.