In 1926, in her second attempt to swim across the English Channel

One imp thing please don't cross options containing not only...but
always check for parallelism

NOT ONLY X...BUT Y is also correct

one gmat prep question:

By pressing a tiny amount of nitrogen between two diamonds to a pressure of 25 milliion pounds per square inch, scientists not only were able to transform the gas into a solid, but they also created a semiconductor similar to silicon

A. not only were able to transform the gas into a solid, but they also created
B. not only were able to transform the gas into a solid but also creating
C. were able not only to transform the gas into a solid but to create
D. were able not only to transform the gas into a solid but also creating
E. were able not only to transform the gas into a solid but they were also able to create

the correct answer is c, the only choice that features proper parallelism.


Similarly :
In 1926, in her second attempt to swim across the English Channel, Gertrude Ederle not only
crossed the Channel against currents that forced her to swim thirty-five miles instead of the
minimal twenty-one, but she set a record for speed as well, by swimming the distance in almost
two hours faster than anyone had yet done.

A. but she set a record for speed as well, by swimming the distance in almost two hours faster than
anyone had yet done.

B. but also set a record for speed, swimming the distance almost two hours faster than anyone had
yet done. ->correct parallelism not only crossed but also set
C. but also swam the distance in almost two hours faster than anyone had yet done, and setting a
record for speed.
D. but also setting a record for speed by swimming the distance in almost two hours faster than
anyone had yet done.
E. but, swimming the distance almost two hours faster than anyone had yet done, she also set a
record for speed.