题目内容：

BUS SERVICE
New York City-Brennan,New Jersey
（Trip time:30 minutes each way）
Timetable
●Buses leave the Railway Station,New York 7:00 am and every half-hour thereafter（此后）until1 11:30 pm （7days a week）.
●Buses leave Brennan Station 20 minutes before and after every hour from 6:20 am to 10:40（7days a week）.
●Evening rush hours（5:00 pm to 7:00 pm）buses leave the Railway Station,New York every 15minutes（Monday-Friday）.
●Holidays:buses leave every hour on the hour time,each direction.
All tickets must be bought at Window 12,the Railway Station,New York,or at the Brennan Station Window before boarding buses.
What time does a bus leave New York for Brennan on Thursdays?
A．10:20 am B．6:30 am C．6:45 am D．4:40 am
能说明一下为什么选B吗?