Since marathons are a challenge for me, I signed up to run two races so that i can prove to myself i can do it! A) simple B) compound C) Complex D) Compound-Complex

The answer is C: Complex

A Compound sentence unites two or more independent clauses using a coordenator (for, so, and etc). A Complex sentence has one independent clause and one or more dependent clauses. And a Compound-Complex unites a Compound sentence with a Complex Sentence.

Since marathons are a challenge for me, (dependente clause)

I signed up to run two races (independent clause)

so that I can prove to myself I can do it. (dependent clause)

It is D) Compound - Complex I just took the test and I got this question right.