Iam the 1st on earth ,the 2nd in heaven ,i appear 2 times in a week , you can only see me once in a year although i am in the middle of the sea, what am i?

The  franco-prussian  war, a  war  that was  led by prussia a coalition of  german  states, defeated  france. the  war  was the end  of  french  hegemony in europe and resulted in a unified  germany.  i hope this !

Physical systems is the answer

Either b or c . i did this before