Please answer quickly

Which best describes the suspense technique of flashback? an image, color, object, or similar is shown early in the film. it later reappears in a pivotal scene or plot point. details of the story outside of the chronological storyline are provided to the audience, often as a memory. illusions of explosions and other events are presented, often using computer-generated imagery to seem realistic. the screenwriter lets the audience know something the main character does not, usually something important to the plot.

Dogs make wonderful pets because they us stay happy and healthy. the topic sentence is "dogs make wonderful pets." , is this correct? i keep doubting myself.

Need some on this. which answer is it?