Explanation

As printed, sin1°···sin89° is a tiny positive number matching no option. The key B = 1 corresponds to the classic product tan1°···tan89° = 1 (pairing tan k°·tan(90°−k°) = 1 for k = 1…44 leaves tan45° = 1) — 'sin' is likely a transcription error in the stem. Note: key disputed — verify against the official UPSC key.