Because of the phrase of duration, 'since 1920', B should read 'has lost'. The past continuous in C merely emphasizes the continuous loss of money (which, at $200/year, seems quite minuscule!)
Should it read "has lost" or "had lost"? I know the word "since 1920" ... but we have to pay attention to the "was losing" too. So I wonder, which one is the correct one has lost or had lost? Thanks for your help!