Question

now it’s time to mix your chemicals. first, pour about 1/4 cup of vinegar into the bowl. then stir in 1 teaspoon of salt. next, place the pennies in the bowl. let them sit in the solution for about five minutes. remove the pennies when they dropdown with options: smell, look, sound bright and shiny.

Explanation:

The sentence is about determining when to remove the pennies based on their appearance (bright and shiny). "Look" is the sense related to visual appearance, while "smell" is for odor and "sound" is for auditory perception, so "look" is the correct choice.

Answer:

look