_________ solution of phenol in water acts as a disinfectant.

The correct answer is Option (1) → 1 %

The same substance can act as an antiseptic or a disinfectant depending on its concentration. Antiseptics are applied to living tissue; disinfectants kill microorganisms on non-living objects such as floors, drains and instruments, and are not safe for living tissue. A 0.2% solution of phenol is an antiseptic, while its 1% solution is a disinfectant.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Antiseptics and Disinfectants – “… Same substances can act as an antiseptic as well as disinfectant by varying the concentration. For example, 0.2 per cent solution of phenol is an antiseptic while its one percent solution is disinfectant.”