ANSWER: I believe the answer is B, but I'm not sure.
Truck Speed Limit Laws: The Complete List. Highway speed limits can range from 35 mph (56 km/h) in urban areas to 85 mph (137 km/h) in rural areas. Typically posted in increments of five miles per hour (mph), truck speed limits are set by either the state or the local counties, municipalities or other local statutes
The answer to the question above is true that the word 'competent' is used correctly in the "it is important to use competent sources when researching" sentence<span>. The word "competent" means a characteristic of acceptable and satisfactory. The sentence above means that it is important to use acceptable sources for a research.</span>