The trian chugs along the tracks as it passes by a river but doesn’t go through a tunnel

Question

Is this a simple sentence
Compound sentence
Complex sentence
Compound complex sentence

Answer 1

This is a simple sentence.

Answer 2

You sure

Answer 3

I apologize for the mistake. This sentence is actually a complex sentence because it contains one independent clause ("The train chugs along the tracks") and one dependent clause ("as it passes by a river but doesn’t go through a tunnel").