What do street lights generally signify?

Answer: B — 30 mph speed limit unless other signs present

Street lights are not typically used to signify specific speed limits. Option A, C, and D are all incorrect as speed limits are usually indicated by separate signs posted on the side of the road. Additionally, street lights are usually used for safety purposes to illuminate roads, sidewalks, and intersections at night rather than for indicating speed limits. Therefore, option B is the best answer as it states that street lights signify a speed limit of 30 mph unless other signs are present. This allows drivers to follow the speed limit on a well-lit road but also be prepared to adjust their speed if they come across a different speed limit sign.