Rearrange the following sentences in the proper sequence to form a meaningful paragraph; then answer the questions given below them.

(A) He discovered many patients were diagnosed before turning 65.
(B) Recently, scientists found a genetic marker tied to early-onset Alzheimer’s.
(C) Alzheimer’s is a brain disorder that damages memory and thinking over time.
(D) Using this lead, Rohan studied data from 48 states in the USA.
(E) This result points to the need for early detection and preventive therapy.
(F) This gradual decline is made worse because most treatments only manage symptoms.

Which of the following should be the THIRD sentence after rearrangement?

To find the correct sequence, let us analyze the links and logical flow between the sentences:

1. Sentence (C) introduces the central subject, Alzheimer's disease, and its nature: "Alzheimer’s is a brain disorder that damages memory and thinking over time." This is the best starting sentence.
2. Sentence (F) links back to the damage mentioned in (C) by using the phrase "This gradual decline": "This gradual decline is made worse because most treatments only manage symptoms." Therefore, (F) is the second sentence.
3. Sentence (B) introduces a new development in research: "Recently, scientists found a genetic marker tied to early-onset Alzheimer’s." This serves as the third sentence.
4. Sentence (D) refers to the finding in (B) using the phrase "Using this lead": "Using this lead, Rohan studied data from 48 states in the USA." This makes (D) the fourth sentence.
5. Sentence (A) details the findings from Rohan's study mentioned in (D): "He discovered many patients were diagnosed before turning 65." This is the fifth sentence.
6. Sentence (E) concludes the paragraph by referencing the findings ("This result") and suggesting a next step: "This result points to the need for early detection and preventive therapy." This is the sixth sentence.

The correct logical order of the sentences is C - F - B - D - A - E.

Thus, the third sentence in the rearranged paragraph is B.