Which of these sentences is punctuated correctly?
 a. Although the concert doesn't start for over an hour; most of the fans have already arrived at the concert hall. 
b.The concert doesn't start for over an hour; though, most of the fans have already arrived at the concert hall. 
c.Most of the fans have already arrived at the concert hall; however, the concert doesn't start for over an hour. 
 d.Even though the concert doesn't start for over an hour; however, most of the fans have already arrived at the concert hall.