Which is a compound sentence?
i managed to complete the task, but i missed the deadline.
my brother, who has always played baseball, earned a sports scholarship to college.
while studying for the test, marisa realized she was not prepared.
the man who called tonight wants us to hire him to remodel our bathroom.

The correct answer is - I managed to complete the task, but I missed the deadline.

A compound sentence is a sentence that contains more than one independent clause (if there is only one independent clause, then the sentence is simple; if there are dependent clauses involved as well, then the sentence is complex). The only option among these which is compound is the first option - the other ones are complex sentences rather than compound.

at hatfield elementary school, there are 504 students in 7 classes. each class has the same number of students. what is a good estimate of the number of students in each class?