Likewise , if all columns as well as the two top rows are exact , then the bottom row is exact as well .
is a commutative diagram and all columns as well as the two bottom rows are exact , then the top row is exact as well .
If all columns as well as the two top rows are exact , then the bottom row is exact as well .
is a commutative diagram and all columns as well as the two bottom rows are exact , then the top row is exact as well .