Official Solution:
Since the official process of naming hurricanes and tropical storms, using the World War II phonetic alphabet, began in 1945, female names were not used until 1953 when the phonetic system was replaced.
A. Since the official process of naming hurricanes and tropical storms, using the World War II phonetic alphabet, began in 1945, female names were not used until 1953 when the phonetic system was replaced.
B. Although the official process of naming hurricanes and tropical storms, using the World War II phonetic alphabet, began in 1945, female names were not used until 1953 when the phonetic system was replaced.
C. When the World War II phonetic system was replaced, female names were used to name hurricanes and tropical storms in 1953 to replace the phonetic alphabet system, which began in 1945.
D. Female names were not used to name hurricanes and tropical storms until 1953 by replacing the World War II phonetic alphabet system that was the official process that started in 1945.
E. The official process of naming hurricanes and tropical storms began in 1945 and used a system based on a World War II phonetic alphabet; this phonetic alphabet system was replaced in 1953 by female names.
A review of our answer choices shows we must choose where the dependent clause in the sentence should be placed, where a participial phrase (acting as an adjective) should be placed, and which subordinating conjunctions should be used.
Since the entire sentence is underlined, let's review our answer choices one at a time.
Option A has a participial phrase describing the official process of naming hurricanes (using a World War II phonetic alphabet). This adjective phrase is not essential to the meaning of the sentence and can safely be ignored for now. The prepositional phrase "of naming hurricanes and tropical storms" modifies the noun "official process." We can safely ignore this prepositional phrase since we now know what the "official process" is about. Without these modifying phrases, our sentence reads "Since the official process began in 1945, female names were not used until 1953 when the phonetic system was replaced. This sentence uses the subordinating conjunction "since." "Since," when used as a conjunction, can mean 1) "because of the fact that" or 2) "up to the present time from a time in the past." "Female names were not used up to the present time the official process began in 1945." That doesn't make much sense. "Female names were not used because of the fact that the official process began in 1945." "Female names were not used" does not make sense with either meaning of "since." This option cannot be the correct answer.
Option B is identical to Option A except it uses the subordinating conjunction "although." "Although" means "even though" or "in spite of the fact that." "Female names were not used even though the official process began in 1945." That makes sense. "Female names were not used in spite of the fact that the official process began in 1945." That also makes sense. "Although" is an appropriate subordinating conjunction for this sentence. This could be the best answer. Let's set it to the side for the moment.
Option C uses the subordinating conjunction "when." "When" means "at the time that." "Female names were used at the time that the World War II phonetic system was replaced." That makes sense. "Which began in 1945" is a non-essential relative clause describing the phonetic alphabet system, and the clause is correctly placed by the noun it is modifying. The prepositional phrase "in 1953" is awkward. It is unclear what it is modifying. Additionally, the word "replaced" is repeated in close proximity in the sentence and the term "phonetic system" is repeated as well. This sentence lacks concision and has an unclear prepositional phrase. This cannot be the best answer.
Option D used the relative pronoun "that" twice in the sentence to create essential relative clauses that modify the prepositional phrase, but they are not necessarily essential to the sentence. This creates a wordy and awkward sentence. Additionally, the prepositional phrase "by replacing the World War II phonetic alphabet system" is trying to act like an adverb modifying the action "female names were not used" by answering the question "how?" But, the prepositional phrase doesn't clearly answer how "female names were not used." This sentence is unclear and awkward. It cannot be the best answer.
Option E is two independent clauses connected by a semicolon. While there is nothing technically wrong with the sentence, it is wordy. It uses two sentences when one would suffice. It also needlessly repeats "phonetic alphabet." This cannot be the best answer.
We have successfully eliminated four answer choices. Option B is the best answer.
Answer: B