Помогите никак не могу определится это 5 или 18 предложение.

Вот задание:
Найдите в тексте предложение с причастием 1 и инфинитивом.
Вот текст:
​1. Oxygen was first discovered by Swedish pharmacist Carl Wilhelm Scheele who realized that air is a mixture of substances, one of which is a life-giving substance.
2. He had produced oxygen gas while heating mercuric oxide and various nitrates by about 1772, but his finding was not published until after the independent discovery by Joseph Priestly.
3. Joseph Priestly found that the gas he discovered could support combustion for longer than ordinary air.
4. The name of oxygen was created by Antoinie Laurent Lavoisier.
5. He used experiments on oxidation to prove that substance discovered by Priestley and Scheele was a chemical substance.

6. Isolating oxygen from air Antoinie Lavoisier emphasized the role of oxygen in combustion and respiration.
7. He was the first to give explanation of combustion.
8. Perhaps the most familiar reaction of oxygen with other materials is combustion.
9. Some of Lavisher’s most important experiments examined the nature of combustion or burning.
10. Through these experiments, he demonstrated that burning is a process that involves the combination of a substance with oxygen.

11. Oxygen is the third most abundant chemical element in the universe, after hydrogen and helium.
12. All air breathing microorganisms would die within a few minutes if the supply of oxygen in the atmosphere stopped suddenly.
13. The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle.
14. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere.
15. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth's atmosphere.
16. Photosynthesis releases oxygen into the atmosphere, while respiration and decay remove it from the atmosphere.

17. Oxygen is a highly reactive element and is able to combine with most other elements.
18. It is essential for human life because most of the chemical activities to be taken in the cells can occur only in the presence of oxygen.
19. Combining with an element, oxygen forms a product called an oxide.

20. Water is the oxide of hydrogen and the most abundant oxygen compound.
21. Some elements readily form oxides at standard conditions for temperature and pressure.
22. The surface of aluminum and titanium are oxidized in the presence of air.
23. Thin film of oxide coating them protects the metal and slows corrosion.

24. Oxygen can be produced through the electrolyses of water.
25. Uses of oxygen include the production of steel, plastics and textiles, oxygen therapy, spaceflights and diving.
26. Oxygen therapy is used to treat pneumonia and heart disorders.
27. There are many organic solvents that contain oxygen, including: acetone, methanol, ethanol, acetic acid and formic acid.

​28. Oxygen, silicon, aluminum and hydrogen together constitute approximately 80 percent of the Earth’s crust.

Что-то я не вижу причастия в 18 предложении, где оно там?