Air is mainly composed of nitrogen, oxygen, and argon, which together constitute the major gases of the atmosphere. Water vapor accounts for roughly 0.25% of the atmosphere by mass.
Physical property, such as real estate, does not qualify due to the unpredictable length of the sales process. As retirement accounts, 401(k)s and IRAs operate both as liquid assets and non-liquid assets depending on the circumstance.
In a classified balance sheet, assets are usually classified as: (a) current assets; long-term assets; property, plant, and equipment; and intangible assets. (b) current assets; long-term investments; property, plant, and equipment; and common stock. (c)