Answer:
It is a compound-complex sentence
Explanation:
To answer this question we need to understand what the definitions are:
A simple sentence has just one independent clause or one complete thought. It has one subject, one verb, and modifiers.
A complex sentence has one independent clause (one subject, a verb, its modifiers, and a complete thought; this sentence can stand alone) and one dependent clause (it doesn't have a complete thought, it depends on the independent clause).
A compound sentence has two independent clauses, they can stand alone, both of them have a complete thought, and they are joined by coordinating conjunctions 'and', 'but', 'or'.
A complex-compound sentence has two independent clauses that can stand on their own without losing a complete thought, and one dependent clause (it can't stand alone; it depends on the independent clause).
So let's look at the given sentence:
This impact was felt from the bottom up, and these contributions to
American institutions may be the ones which most intimately affect the
lives of all Americans.
We can see that the first clause is independent - This impact was felt from the bottom up - it has a complete thought; it can stand alone.
The other clause is also independent - and these contributions to
American institutions may be the ones - it has a complete thought; it can stand alone; it is connected to the other clause with coordinating conjunction 'and'.
The last clause is the dependent clause - which most intimately affects the lives of all Americans - it can't stand alone; it doesn't have a complete thought. To be exact it is an adjective clause, it explains the noun 'contributions' or the pronoun 'one'.
So, we have two independent clauses and one dependent. It is a complex-compound sentence.
I hope it helped you :)
