In order to conserve the energy and heat they need to spend the entire winter sitting motionless over incubating eggs, male emperor penguins huddle over the nests in groups, thereby reducing the rate at which they burn energy so that it is 25 percent lower than it would be for isolated birds.
(A) thereby reducing the rate at which they burn energy so that it is 25 percent lower than it would be for
(B) thereby reducing their rate of burning energy until it is 25 percent lower when compared with
(C) and they thereby reduce by 25 percent the rate they burn energy, as compared to what it would be with
(D) which thereby reduces by 25 percent their rate of burning energy, when comparing them to
(E) which thereby reduces the rate they burn energy so that it is 25 percent lower than
(A) thereby reducing the rate at which they burn energy so that it is 25 percent lower than it would be for
(B) thereby reducing their rate of burning energy until it is 25 percent lower when compared with
(C) and they thereby reduce by 25 percent the rate they burn energy, as compared to what it would be with
(D) which thereby reduces by 25 percent their rate of burning energy, when comparing them to
(E) which thereby reduces the rate they burn energy so that it is 25 percent lower than
