Pls asap will give brainlest as a fire truck approached mary, the pitch of the siren got higher. once the fire truck passed and moved away, the siren's pitch got lower. this change in pitch is because of a change in the sound wave's 1. concussion 2. frequency 3. amplitude 4. reflection

Which of the following situations is impossible? a) an object has velocity directed east and acceleration directed east. b) an object has zero velocity but non-zero acceleration. c) an object has constant non-zero velocity and changing acceleration. d) an object has velocity directed east and acceleration directed west. e) an object has constant non-zero acceleration and changing velocity.