UPSC Prelims 2020— Question 3

This question tests lisa and gravitational-wave detection. The key concept is: The described triangular formation with million-kilometre arms refers to the Laser Interferometer Space Antenna concept, or evolved LISA, designed to detect low-frequency gravitational waves in space. LISA Pathfinder was a technology demonstrator rather than the full three-spacecraft observatory. The verified answer for the uploaded Set-B paper is option D. Option A — Voyager – 2: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: The described triangular formation with million-kilometre arms refers to the Laser Interferometer Space Antenna concept, or evolved LISA, designed to detect low-frequency gravitational waves in space. LISA Pathfinder was a technology demonstrator rather than the full three-spacecraft observatory. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option B — New Horizons: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: The described triangular formation with million-kilometre arms refers to the Laser Interferometer Space Antenna concept, or evolved LISA, designed to detect low-frequency gravitational waves in space. LISA Pathfinder was a technology demonstrator rather than the full three-spacecraft observatory. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option C — LISA Pathfinder: This is not the correct option. The option does not match the verified combination or conclusion. The decisive point is the distinction explained above: The described triangular formation with million-kilometre arms refers to the Laser Interferometer Space Antenna concept, or evolved LISA, designed to detect low-frequency gravitational waves in space. LISA Pathfinder was a technology demonstrator rather than the full three-spacecraft observatory. Therefore this alternative should be eliminated even if part of its wording appears plausible in isolation. Option D — Evolved LISA: This is the correct option. It matches the verified conclusion because The described triangular formation with million-kilometre arms refers to the Laser Interferometer Space Antenna concept, or evolved LISA, designed to detect low-frequency gravitational waves in space. LISA Pathfinder was a technology demonstrator rather than the full three-spacecraft observatory. The wording of the option is consistent with the governing concept tested by the question. For UPSC-style elimination, first identify the exact proposition being tested, then evaluate each statement independently before comparing the answer codes. Avoid treating a broad or absolute statement as correct merely because its general theme is familiar. The precise qualifiers in the question—such as 'all', 'only', 'cannot', 'largest', 'always' or a specific institutional role—often determine the answer. On that basis, option D is the verified answer.