For ease of reading, the form Rs is less confusing than rs. Example:
"Railroad crossing look out for cars. Can you spell it without any Rs?"
R's is the plural form of r, but Rs is acceptable although not the preferred form.
The plural of "Rs" can be either "Rs" or "rupees", depending on the context.
Rupees - Rs. (plural) Re. (Singular) Paise - p
ar is not a letter. R is a letter. The plural would be Rs.
There is no plural form. Do and Do not are verbs
The plural form of him, her, or it is them. (objective pronouns)
Bridges is the plural form of bridge.
The plural form of "is" is "are."
The plural form of "I" is "we."
The plural form of "was" is "were."
"Groceries" is the plural form of "grocery."
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.