Question

Read the sentences.

The Mississippi River flows from Minnesota to the Gulf of Mexico. Its source is a peaceful lake in Minnesota. It flows south. It flows past 10 states. Its mouth is in Louisiana.

Which sentence best combines these ideas into a compound-complex sentence?

After rising from a peaceful lake in Minnesota, the Mississippi River flows south past 10 states and empties into the Gulf of Mexico.
The Mississippi River flows south from a peaceful lake in Minnesota past 10 states to empty into the Gulf of Mexico at its mouth in Louisiana.
The Mississippi River, the source of which is a peaceful lake in Minnesota, flows south past 10 states and empties into the Gulf of Mexico at its mouth in Louisiana.
The source of the Mississippi River is a peaceful lake in Minnesota; from there, the river flows south past 10 states to its mouth in Louisiana, where it empties into the Gulf of Mexico

Answer 1

The fourth sentence.

It has two independent clauses ("The source... is a peaceful lake in Minnesota;" and "from there, the river flows... to its mouth in Louisiana") plus the dependent clause "where it empties into the Gulf of Mexico," so it is compound-complex.