The correct answer is: A. PQRS
The world’s fastest computers were initially conceived for military purposes. However, they are now finding various new uses, such as as environment tools.
Option B, QPSR, is incorrect because the sentence should start with the main idea, which is that the world’s fastest computers were initially conceived for military purposes. Option C, RPSQ, is incorrect because the sentence should not end with the main idea. Option D, SQRP, is incorrect because the sentence should not start with a subordinate clause.