A reactive windshear warning system detects windshear by measuring:

Changes in the aircraft's energy state through accelerometer and air data inputs

Correct

Changes in outside air temperature only

Doppler radar returns

Wind speed from ground-based sensors

Explanation

Reactive windshear detection uses inertial and air data to detect sudden changes in the aircraft's energy state indicative of windshear encounter.

Test yourself with random questions from Operational Procedures and all other ATPL subjects.