Question

which sentence is an example of how a scientist might use a model?
marbles placed inside a hollow sphere are used to describe protons in a nucleus.
stopwatches measure the amount of time it takes for runners to complete a mile.
a wrench is used to tighten a nut onto a piece of wood.
microscopes are used to magnify a group of cells on sets of slides.

Explanation:

A model is a representation to explain a concept. Marbles in a hollow sphere represent protons in a nucleus as a model. The other options are about measurement (stop - watches), tool - use (wrench), and magnification (microscopes), not model - use.

Answer:

Marbles placed inside a hollow sphere are used to describe protons in a nucleus.