Which aircraft had mission-adaptive wings?

The B-1B Lancer is known for its mission-adaptive wings, which allow the aircraft to optimize its performance for various flight conditions and mission profiles. These variable-sweep wings can change their angle during flight, which enhances maneuverability at different speeds and altitudes. This capability is particularly beneficial for a bomber aircraft like the B-1B, as it allows for effective low-level flight as well as efficient high-speed cruising.

The other options represent aircraft with different design philosophies: the AD-1 Scissors is notable for its unique wing design but not mission-adaptive capabilities, the X-29A utilized a forward-swept wing design to explore advanced aerodynamic concepts but did not have mission-adaptive wings, and the XB-15 was an early heavy bomber with a fixed-wing configuration. The technology of variable wing sweep seen in the B-1B distinguishes it from these other aircraft, making it the correct choice regarding mission-adaptive wings.