Step 1: Understanding the clues.
Each clue forms a meaningful phrase with “mark”: birthmark, pockmark, examination mark, and benchmark. These are all standard and widely used expressions.
Step 2: Evaluate each option.
(A) Certificate – Only connects with birth (birth certificate).
(B) Pox – Matches only pock (pock-pox).
(C) Test – Matches examination, but not others.
(D) Desk – Matches bench (bench–desk relation), but not all clues.
(E) Mark – Matches all four clues meaningfully.
Step 3: Conclusion.
“Mark” is the only word forming correct and meaningful expressions with all clues.