Why do we have nightmares...???

Which of the following is considered to be a vector?               a.  temperature    b.  velocity    c.  time    d.  mass

20. threshold braking in the vehicle's braking system occurs when a. the brake pedal is pushed, heel on floorboard, with full foot pressure. b. the brakes are exerting full braking power, without traction loss. c. the driver begins pushing down the brake pedal, with moderate slowdown. d. the brakes just begin to take hold with a gradual slowdown.

How are positive ions different from neutral atoms