It is true that 70% or so of the Air is nitrogen but that it needs to be the largest reservoir. Nitrogen is an essential part of most living organisms. Most of the bodily fluids and enzymes have nitrogen in a bonded form. This is true even in the case of plants. So, the correct answer is "Air".

"Ozone hole" means thinning of the ozone layer.

The nitrogen molecules present in the air can be converted into nitrates and nitrites by nitrogen fixation.

Reformation of ozone in stratosphere is powered by UV radiation.

The part of the atmosphere which contains constant gases with a known composition called homo-sphere.

Plant consume carbon dioxide, water and other nutrients to make their own food.

Solid oxygen is a clear substance with a light sky-blue colour. Oxygen gas is a colourless gas without taste or odour. Oxygen toxicity is a condition that results from the harmful effects of breathing molecular oxygen $(O _2)$ at elevated partial pressures. This causes hyperoxia, an excess of oxygen in body tissues.

Oxygen is produced by plants by the process of photosynthesis,

Plants plays a very important role in the oxygen cycle as plants create the majority of oxygen we breathe through the process of photosynthesis. In this process plants use $CO _2,$ sunlight and water to create energy. In this process they also create oxygen which they release into the air.

Plants also consume oxygen for respiration.

Heavy water violence is formed on combining deuterium with oxygen.