The plural is aspirins.
The singular form of "aspirin" is "aspirin." It's one of those words where the singular and plural are the same!
Aspirin is acetylsalicylic acid. Consequently, it can act as a Lewis acid. Ammonia is a Lewis base. Therefore, ammonia and aspirin can react to form the ammonium salt of aspirin.
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.
"Groceries" is the plural form of "grocery."
The plural form of "meter" is "meters."
It has no plural form.
The plural form for the noun sergeant is sergeants; the plural possessive form is sergeants'.
The plural form of rung is rungs.
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 of "she" is "they", so the plural of "she had" is "they had".