Inside a residential district, what is the speed limit?

Answer: A — 20 mph

The speed limit inside a residential district is typically 20 mph to ensure the safety of the residents and decrease the chances of accidents. While option B (25 mph) may seem like a reasonable speed, it can still pose a risk to pedestrians and other vehicles. Option C and D (30 mph and 35 mph) are often the speed limits for urban or suburban areas, which have more lanes and less pedestrian traffic compared to residential areas. Therefore, option A is the best answer as it is the standard and recommended speed limit for residential districts.