5) Since companies are rethinking their portfolios for the post crisis world, they should ask themselves if they are still the best owner of their assets.
(A) Since companies are rethinking their portfolios for the post crisis world, they should ask themselves if they are still the best owner of their assets. -- Here whether should be used instead of If. Wrong
(B) As companies rethink their portfolios for the post crisis world, they will ask themselves if they still continue to be the best owner of their assets -- changes meaning by using will instead of should. Wrong
(C) As companies rethink their portfolios for the post crisis world, they should ask themselves whether they are still the best owners of their assets --CORRECT. "Whether is correctly used. As companies rethink …, they should ask themselves .." No contrast is intended in this sentence.
(D) As companies rethink their portfolios for the post crisis world, each of them should ask themselves if they are still the best owners of their assets-- Sub-verb error. each of them is singular. Wrong
(E) Although companies rethink their portfolio for the post crisis world, they should ask themselves whether they are still the best owners of their assets -- Although is used to add contrast, but their isn't any in this sentence. Wrong usage.
(A) Since companies are rethinking their portfolios for the post crisis world, they should ask themselves if they are still the best owner of their assets. -- Here whether should be used instead of If. Wrong
(B) As companies rethink their portfolios for the post crisis world, they will ask themselves if they still continue to be the best owner of their assets -- changes meaning by using will instead of should. Wrong
(C) As companies rethink their portfolios for the post crisis world, they should ask themselves whether they are still the best owners of their assets --CORRECT. "Whether is correctly used. As companies rethink …, they should ask themselves .." No contrast is intended in this sentence.
(D) As companies rethink their portfolios for the post crisis world, each of them should ask themselves if they are still the best owners of their assets-- Sub-verb error. each of them is singular. Wrong
(E) Although companies rethink their portfolio for the post crisis world, they should ask themselves whether they are still the best owners of their assets -- Although is used to add contrast, but their isn't any in this sentence. Wrong usage.