Final answer:
The number of protons in an atom stays the same as you move across a period in the periodic table.
Step-by-step explanation:
As you move across a period in the periodic table, the number of protons in an atom remains the same. The number of protons defines the atomic number of an element, and each element has a unique atomic number. However, the number of electrons in the atom can change, which affects the overall charge of the atom. Therefore, the correct answer is b) The number of protons stay the same.