Carbons is the plural of carbon, when used in the sense of a black sheet used to make a copy.
It is a molecule (not plural). 1 carbon, 2 oxygen (=oxide).
It is a stoma, plural is Stomata.
'Gas' can be both singular and plural depending on context. When referring to a substance like oxygen or carbon dioxide, it is often used as a mass noun and is considered singular. When referring to multiple types of gases or quantities of gas, it is treated as a plural noun.
Stoma (or plural form stomata for a number of stoma)
Stoma (or plural form stomata for a number of stoma)
Alveoli (plural) and alveolus (singular)
One alveolus is a singular, tiny air sac of the lung, surrounded by a network of capillaries, and through which oxygen and carbon dioxide are exchanged. A cluster of such air sacs are alveoli (plural of alveolus).
The plural of 'this' is 'these' and the plural of 'that' is 'those'.
Isthmi is plural. There are actually two plural forms. I will list them from singular to plural. Isthmus - Singular Isthmi - Plural Isthmuses - Plural
The plural of rose is roses. The plural possessive is roses'.
The plural of 'bunch' is bunches.The plural of 'ant' is ants.The plural of 'batch' is batches.The plural of 'day' is days.The plural of 'chimney' is chimneys.The plural of 'tomato' is tomatoes.The plural of 'umbrella' is umbrellas.The plural of 'donkey' is donkeys.The plural of 'sky' is skies.The plural of 'foot' is feet.The plural of 'show' is shows.
The plural form of can is cans.