Having observed the icebergs in Antarctica for over a decade,
their melting rate is no longer considered to be constant by Dr.Eric Godert, it is increasing rapidly, raising the mean sea water level.
A.
their melting rate is no longer considered to be constant by Dr.Eric Godert, it is increasing rapidly, raising : After comma, we need the subject who observed the icebergs.
B.
their rate of melting is no longer considered to be constant by Dr.Eric Godert, it is increasingly rapid and raising : Same error as in A
C. Dr. Eric Godert considers their rate of melting no longer constant but increasing rapidly, raising : CORRECT
D. Dr. Eric Godert
considers their melting rate to be no longer constant but one that is increasing rapidly, raising : Consider to be wrong.
E. Dr. Eric Godert
considers their rate of melting to be increasingly rapid and no longer constant, raising : Consider to be wrong.