The correct answer would be B, since complex sentences have 1 independent variable and one dependent variable.
The dependent variable would be: Everytime he hears a siren
Why? Because it is not a complete thought.
The independent variable would be: My dog howls loudly.
Why? This statement is a complete thought.
A would be a compound sentence
C would be a simple sentence
D would be compound complex.
Hope I could help!
Answer: The answer choice that I would best conclude as correct would be letter 
Explanation: Hope this helps! Have a wonderful day! <3
Answer: The answer is D
Explanation: The rest of the answers don’t correlate to the story that well, D says how he found a mainly which makes up for a good climax for this story.
Answer:
A
Explanation:
The rest of the answers contradict themselves
