#### Answer

(a) Scalar
(b) Vector
(c) Vector
(d) Scalar

#### Work Step by Step

(a) The cost of a theater ticket is a number , it does not have a direction . Thus it is a scalar.
(b) The speed of the flow of the river tells about its magnitude and which direction the current is going is the direction. Thus, the current in the river has bot magnitude and direction , so it is a vector.
(c) The initial flight path has a direction form Houston to Dallas and a magnitude (how far) . Therefore, it is a vector.
(d) The population of a world is a number , so it has magnitude only; not direction. Thus, it is a scalar.