GMAT and CAT both require strong foundation in English Grammar.See what i just did ,i gave equal importance to both gmat and cat.
Some bat caves, like honeybee hives, have residents that take on different duties such as defending the entrance, acting as sentinels and to sound a warning at the approach of danger, and scouting outside the cave for new food and roosting sites.
(A) acting as sentinels and to sound
(B) acting as sentinels and sounding
(C) to act as sentinels and sound
(D) to act as sentinels and to sound
(E) to act as a sentinel sounding
here all except B violate parallelism by using the infinitve to
check out how defending and scouting(present participial) are in parallel ,so sounding is the best answer.InE sentinel is singular not in sync with residents(subject verb agreement).
The only way for growers to salvage frozen citrus is to process them quickly into juice concentrate before they rot when warmer weather returns.
(A) to process them quickly into juice concentrate before they rot when warmer weather returns
(B) if they are quickly processed into juice concentrate before warmer weather returns to rot them
(C) for them to be processed quickly into juice concentrate before the fruit rots when warmer weather
(D) if the fruit is quickly processed into juice concentrate before they rot when warmer weather returns
(E) to have it quickly processed into juice concentrate before warmer weather returns and rots the fruit
The only way .. to salvage X ...is to process..,now citrus is singular and doesn't agree with them and they ,so setence A is wrong.B,C,D have reference errors ,E is best as it uses parallel infinitives and uses fruit to directly refer to citrus.
References :Manhattan SC
Official Guide for GMAT