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!
im going to read it then get back to you
My favorite movie is Paper Towns, and my favorite character in the movie is Margo
The answer is false but you may want a second opinion