I believe it is a compound sentence
I think it will be A.classmates;to persuade that will be the answer.
Answer:
The indirect object I believe would be "us"
Explanation:
An easy way to remember the indirect object, is to tell yourself that it is the recipricant of the direct object. The direct object in this case would be <em>solution</em>, and the term "us" would be recieving that. Who recieved the solution? Us.
Is there text we can refer from?