Disadvantages and advantages of digit and analog signals

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.

Most short-period comets do not have randomly oriented orbits because

Which compound is held together by the electrostatic force between two ions? a. co2 b. cci4 c. h2s d. mgf2