What is ‘Greased Lightning-10 (GL-10)’, recently in the news?

The correct answer is A. Greased Lightning-10 (GL-10) is an experimental electric aircraft developed and flight-tested by NASA's Langley Research Center. It is a scaled-down, unmanned tilt-wing prototype with ten electric motors, which is where the name comes from. It uses distributed electric propulsion, so it can take off and land vertically like a helicopter and then transition to forward flight like an airplane.

Why the others are wrong:

• B is wrong. Japan has no such GL-10 solar aircraft. Solar-powered flight is a different technology, and the name does not match.
• C is wrong. China's space observatories are named differently. GL-10 is an aircraft, not a space asset.
• D is wrong. ISRO has not designed any reusable rocket called GL-10. Its reusable launch vehicle work has a different name and purpose.

The core concept is electric and distributed propulsion, along with vertical take-off and landing (VTOL) design. For Mains, this links to green aviation, urban air mobility, and the limits of battery energy density that still constrain electric flight.

Trap: Aspirants often associate 'Greased Lightning' with space or ISRO because of the aerospace context, and pick D. Remember that the question is about an aircraft, and NASA has tested it.