Though viewed from a distance, Saturn's main rings may appear to be smooth and continuous, they are in fact composed of thousands of separate icy ringlets when viewed up close.
(a) Though viewed from a distance, Saturn's main rings may appear to be smooth and continuous, they are in fact composed of thousands of separate icy ringlets when viewed up close.
(b) Though Saturn's main rings may appear smooth and continuous when viewed from a distance, they are in fact composed of thousands of separate icy ringlets when viewed up close.
(c) Saturn's main rings, when viewed from a distance, may appear to be smooth and continuous, though when viewed up close they are in fact composed of thousands of separate icy ringlets.
(d) When viewed from a distance, Saturn's main rings may appear smooth and continuous, but closer viewing reveals them to be composed of thousands of separate icy ringlets.
(e) Though composed of thousands of separate icy ringlets if viewed up close, the main rings of Saturn may appear smooth and continuous when they are viewed from a distance.
The original sentence introduces the main clause with "though viewed from a distance", which establilshes the expectation of a contradiction that never materializes. For example, "Though sleepy, the child stayed awake" is correct, whereas "Though sleepy, the child may have eaten soup" is not. Also, "when viewed up close" is placed in such a way as to illogically suggest that the rings are composed of icy ringlets as a result of being viewed up close. Finally, "appear to be" is redundant.
(A) This choice is incorrect as it repeats the original sentence.
(B) This choice incorrectly introduces the main clause with "though." Additionally, the placement of "when viewed up close" illogically suggests that the rings are composed of icy ringlets as a result of being viewed up close.
(C) This choice incorrectly uses the redundant phrase "appears to be." Additionally, the use and placement of the words "when viewed up close, they are . . ." illogically suggests that the rings are composed of icy ringlets as a result of being viewed up close.
(D) CORRECT. This choice replaces "though" with "when" and shortens "appear to be" to "appear." Further, its use of the phrase "closer viewing reveals" clearly indicates that the close viewing only reveals (not causes) the composition of the rings.
(E) This choice incorrectly introduces the main clause with "though." Additionally, the placement of "if viewed up close" illogically suggests that the rings are composed of icy ringlets as a result of being viewed up close.
I'm not sure why I cannot use choice b. It seems like using though in this case should make sense.
Reshma :)