PIMSO 2022 - Science - Grade 8 - National Round Question 12

One forefront in the development of environmentally-friendly automobiles is the search for new fuels from renewable sources. In 2008, the airplane manufacturing company Boeing tested a small aircraft powered by a hydrogen fuel cell. In this fuel cell, hydrogen is reacted with oxygen, producing water, as a source of energy. Which of the following is true?

Terminology note: interpret “addition” here in the source’s broad combination/synthesis sense.