I would say the correct answer is "octane". It is important that you use the fuel with the correct octane rating recommended by the manufacturer. Among the choices it is only octane that is used as a rating for fuels. Hope this helps.
In the font options there is a checkbox for strikethrough. Same dialog as word, only there is no button in the ribbon for it. You could customize that by creating a custom group if you want to.
Answer:
a medical journal/study from a licenced doctor on a website with .org
Explanation:
most medical journals from licenced doctors have .org in the end and are trusted