Although the knee joint is susceptible to many types of injuries, traumatic dislocation is rare; rather ligament injuries are much more common.

A. is rare; rather ligament injuries are much more common
B. is rare, but rather it is ligament injuries that are much more common
C. is rare; rather it is ligament injuries that are much more common
D. is rare; however, ligament injuries are much more common
E. is rare; however, ligament injuries are most common

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IMO D

A. is rare; rather ligament injuries are much more common--wrong, SV are correct, but use of rather after is not correct, because ; is used to seperate 2 IC where adverb can be used at start
B. is rare, but rather it is ligament injuries that are much more common----wrong, SV are correct, Usage of BUT rather is wrong leads to redundancy
C. is rare; rather it is ligament injuries that are much more common----wrong, SV are correct, usage of rather after semi colon is wrong
D. is rare; however, ligament injuries are much more common---correct
E. is rare; however, ligament injuries are most common---wrong, usage of MOST is superlative and changes the meaning
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Official Explanation:

Since the underlined portion of the sentence has a semicolon connecting two clauses, check whether the clauses are connected correctly. In the sentence as written, rather, which implies one thing instead of another, does not correctly connect the two clauses in the sentence or establish the contrast between a rare injury and a much more common type. This is a clauses and connectors error, so eliminate choice A and look for any obvious repeaters. There are no obvious repeaters, so evaluate the remaining answer choices individually, looking for reasons to eliminate each.

Choice B correctly uses the coordinating conjunction but to join the two clauses. However, the word rather does not establish the contrast between a rare injury and a much more common type. This is a clauses and connectors error, so eliminate choice B. Choice C uses the word rather, which does not establish the contrast between a rare injury and a much more common type, so eliminate choice C. Choice D uses however, which correctly connects the two clauses and establishes the contrast between a rare injury and a much more common type, and introduces no new errors, so eliminate choice D. Choice E uses however to correctly connect the clauses and establish the contrasting relationship, but incorrectly uses the comparison word most to compare two items, so eliminate choice E.

Choice A: No. The word rather does not correctly connect the two clauses in the sentence. Clauses & Connectors.

Choice B: No. The word rather does not correctly connect the two clauses in the sentence. Clauses & Connectors.

Choice C: No. The word rather does not correctly connect the two clauses in the sentence. Clauses & Connectors.

Choice D: Correct

Choice E: No. The word most does not correctly compare two items. Quantity words.

The correct answer is choice D.
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