During the upstroke, the wings of a bird move upwards. This is the correct answer because the upstroke is the part of the bird's wingbeat cycle where the wings move in an upward direction.

Explanation:
The wingbeat cycle of a bird consists of two phases: the downstroke and the upstroke. During the downstroke, the wings move downwards, generating lift and propelling the bird upwards. This is the phase where the bird pushes against the air to generate the necessary force for flight.

However, during the upstroke, the wings of the bird move upwards. This may seem counterintuitive, as one might expect the wings to continue moving downwards to maintain lift and propulsion. However, the upstroke serves a different purpose in the flight of birds.

During the upstroke, the bird's wings are brought back up to their original position, ready for the next downstroke. This movement allows the bird to reduce drag and increase efficiency. By raising the wings, the bird minimizes the resistance caused by air pressure and turbulence, making it easier to move through the air.

Additionally, during the upstroke, the tail of the bird may also change its direction. The tail acts as a stabilizer, helping the bird maintain balance and control during flight. As the wings move upwards, the tail may adjust its position to provide the necessary stability.

It is important to note that the movement of the wings during flight is not static but rather dynamic and coordinated. The downstroke and upstroke work together to generate lift and propel the bird through the air. This continuous flapping motion allows birds to achieve sustained flight and maneuverability.

In conclusion, during the upstroke, the wings of a bird move upwards. This movement helps reduce drag and increase efficiency, preparing the wings for the next downstroke. The tail of the bird may also change its direction during this phase to provide stability.

(a) no
(b)