Reagent that converts phenol into picric acid

The same question, asked 3 times: 11 May 2023 S2, 16 May 2023 S2, 25 Apr 2025 S2. Every wording below, oldest first.

Try each one first, then open its answer.

Question 1
11 May 2023 S2
89 $Which from following reagents is used in the conversion of phenol to picric acid?$
Tap an option to check your answer.
Question 2
16 May 2023 S2
75 $Which reagent is used in the conversion of phenol to picric acid?$
Tap an option to check your answer.
Question 3
25 Apr 2025 S2
74 $Which of the following reagents is used in the conversion of phenol into picric acid?$
Tap an option to check your answer.