Rearrange the parts of the sentence in the correct order.

We have been

P. able to identify certain patterns in

Q. the microbiome and immune response

R. that are clearly linked to the progression and

S. severity of brain injury

The correct answer is option 4) i.e. "PQRS." 

Key Points

• In the abovementioned paragraph, there is a chronological sequence of the sentences.
• Sentence P is the first sentence as the paragraph begins with 'We have been.' So we need to use a verb after the helping verb 'have been' and 'able' is a verb.
• Sentence Q is the second sentence as the previous sentence ended with the preposition 'in'. So the next part should start with a noun or pronoun. Among the options, the noun is 'the microbiome and immune response.' Thus it establishes a relation with the previous sentence.
• The only option that shows such an arrangement is Option 4.
• Sentence R is the third sentence as it begins with the pronoun 'that' and creates a relation with the nouns 'the microbiome and immune response' of the previous sentence.
• Finally, sentence S is the last sentence.
• Thus, the correct answer is Option 4.

The correct order is: 

We have been

P. able to identify certain patterns in

Q. the microbiome and immune response

R. that are clearly linked to the progression and

S. severity of brain injury