Isotopes share the same proton number but differ in neutrons.

Steps:

• Identify proton numbers for each atom from the table data (neutral atoms have electrons equal to protons).
• Compare proton numbers: W and X both have 8 protons, while Y has 7 and Z has 9.
• Confirm W and X are isotopes: same protons (8) but different neutrons/mass numbers.
• The element's proton number is thus 8.

Why B is correct:

• Proton number defines the element; isotopes of the same element have identical proton numbers (atomic number 8 for oxygen).

Why the others are wrong:

• A: Matches Y's protons but not the isotopic pair.
• C: Matches Z's protons but not the isotopic pair.
• D: No atom has 10 protons.

Final answer: B