Question

look at the text below. if there is an error with subject-verb agreement, select the incorrect verb and type it correctly. otherwise, submit the text without making any changes. the number of protons in an atom is expressed by that elements atomic number on the periodic table.

Explanation:

The subject "The number of protons" is a singular subject (since "number" is the head noun and it's singular), and the verb "is" agrees with it in number. There is no subject - verb agreement error in the given sentence.

Answer:

The number of protons in an atom is expressed by that element's atomic number on the periodic table.