C
"Jim did not take good notes, but Mary helped him study for the test.'' is a compound sentence.
A compound sentence consists of more than two independent clauses.
An independent clause is one that can stand alone without the other clause.
These independent clauses are joined together using a conjunction such as: and, nor, yet, for, so, and, yet & many more.
In the given sentence, "Jim did not take notes" and "Mary helped him study for the test" are two independent clothes, and each makes sense without the other.
They have been joined together using the conjunction 'but.'
While a simple sentence consists of only one clause It has only one subject, the predicate. A simple sentence may or may not contain an object.
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