The bus that travels from St. Louis to Chicago and back comes to St. Louis every 3 hours while the bus that travels from St. Louis to Springfield and back comes to St. Louis every 7 hours. If at 01:00 o'clock both bused arrived at St. Louis, at what time will they meet in St. Louis again?	Choose the correct choice from the following answers.
A) 16:00.	B) 18:00.	C) 20:00.	D) 22:00.	E) 24:00.
Time taken by bus to travel from St. Louis to Chicago and back comes to St. Louis = 3 hours   Time taken by bus to travel from St. Louis to Springfield and back comes to St. Louis = 7 hours   Time taken by both buses to meet again in St. Louis will be LCM of 3 and 7 = 21   If the buses start at 01:00 o'clock from St. Louis , they will meet again in St. Louis at 22:00 hours   Answer 22:00.
<result>D</result>
The bus that travels from St. Louis to Chicago and back comes to St. Louis every 3 hours while the bus that travels from St. Louis to Springfield and back comes to St. Louis every 7 hours. If at 01:00 o'clock both bused arrived at St. Louis, at what time will they meet in St. Louis again?