In Cold-water habitats, certain invertebrates and fish convert starches into complex carbohydrates called glycerols, in effect manufacturing its own antifreeze.
(A) in effect manufacturing its own antifreeze
(B) effectively manufacturing antifreeze of its own
(C) in effect manufacturing their own antifreeze
(D) so that they manufacture their own antifreeze
(E) thus the manufacture of its own antifreeze
D) so that they manufacture their own antifreeze
I see two problems with D
Usage of so that usually requires a referant. Also, so that usually ends with a conclusion
I need to study grammer so that I get a better verbal score in GMAT
usage of manufacture doesn't fit well with the sentence
On the other hand
in choice C, "in effect manufacturing their own antifreeze" a appositive phrase acts as a modifier keeping the sentence clear.