The percentage of oxygen in NaOH is 40% (Option 1).

Explanation:
NaOH is a white solid inorganic compound also known as Sodium Hydroxide, Lye or Caustic Soda.

As we can see it contains Na, O and H elements with Na+ ion and OH- ion. Coming to oxygens composition, we need to find the total molar mass.

Total Molar Mass of NaOH = 23(Na) + 16(O) + 1(H) => 40

Percentage of oxygen = 16/40 * 100 => 40%.

Thus, th percentage of oxygen in NaOH is 40%