Concept:The correct phrase pair must form a grammatically and contextually meaningful sentence.
Explanation:Check each given combination to see if it makes a proper sentence.
Option A says C-E and A-F.
C-E gives: "The police are under instructions to impound capital punishment is a deterrent." This is incorrect.
A-F gives: "We should never isolate such machines wherever they find them." This is also incorrect.
Option B says A-E: "We should never isolate capital punishment is a deterrent." This is incorrect.
Option C says B-D: "We cannot find is now a dead letter." This is incorrect.
Option D says C-F: "The police are under instructions to impound such machines wherever they find them." This is grammatically and contextually correct.
The word "impound" means to seize or take legal custody of something, which fits perfectly here.
Thus, only C-F forms a valid sentence.
Answer:Option D (C-F)