I think it’s A If Not Correct Me On It But I’m Pretty Sure It’s A
Answer:
Group of concrete nouns is
Library, books, America
Explanation:
Concrete Noun:
Nouns which can be perceived by any one or more of five senses (i.e touch, sight, hearing, taste, smell) are called concrete nouns. In other words things which have a physical existence are called concrete nouns Physical existence does not imply weight and matter only - it can also be light, noise, rainbow etc.
Some obvious examples of concrete nouns are table, room, glass, computer etc.
Opposite to concrete nouns are
Abstract Nouns: These nouns can not be perceived by five senses. They exist only as an idea. e.g wisdom, laziness, beauty etc.
Name of real countries, places, cities are considered concrete nouns. Country/city/town are also concrete nouns so are river, school, college.
Whereas paradise, colleague, angels, life, values, freedom are all abstract nouns.
It’s in the correct order that you listed it 1,2,3,4 because the American revolution is a piece of history. photosynthesis is science. But the number of shoes you own and your best friends childhood memory are personal and wouldn’t be in a library
“i don’t know the answer.” is a clause