You seem to be having trouble with compound words. Which thing do you have more of - ears or muffs? You don't have ears muff because it's not the ear that's the thing, it's the muff - so you say two ear muffs.
Bridges is the plural form of bridge.
"Beliefs" does not have a plural form, as it is already plural. Beliefs is the plural form of belief.
There is no plural form for the word, countries. This word itself is a plural.
The plural of "she" is "they", so the plural of "she had" is "they had".
You seem to be having trouble with compound words. Which thing do you have more of - ears or muffs? You don't have ears muff because it's not the ear that's the thing, it's the muff - so you say two ear muffs.
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.
Earmuff
The plural form of mouth is mouths. The plural form of month is months. The Mounth is a range of hills in Scotland and does not have a plural form.
The plural form of the demonstrative pronoun 'that' is those.