What as modern science determined about racial categories

Late at night some traffic signals change patterns and become ?

17 a tourist was planning a trip by car for travelling at some constant speed for 2.5 hours. however, he found that if he increases the speed by 20 km/h he can cover the same distance in 30 minutes less time than it was planned. what was the planned speed of the tourist, in km/h?

What is another way name for bd? cf, bd, cf, be