Which sentence is punctuated correctly?
A.
Our grandparents are returning home by train; and their departure time is 8:00 A.M.
B.
Our grandparents are returning home by train, their departure time is 8:00 A.M.
C.
Our grandparents are returning home by train; their departure time is 8:00 A.M.
D.
Our grandparents are returning home by train their departure time is 8:00 A.M.