HELP ASAPPP An iron nail was placed in an open test tube containing some salt solution, and then left for a week for observations. The experimental setup and observations are shown below.

Which of the following best demonstrates that a chemical change has taken place?

The salt solution was discolored after a week.

The volume of the salt solution has decreased.

The mass of the salt solution, beaker and nails decreased.

The iron nail is still undissolved in the solution after a week.