mismatched units

Question

Which of the following arrangements of units are considered "mismatched units?"

Select one:

a. (kilowatt)(hour)

b. meter/sec

c. (foot)(pound)

d. kilometer/sec²

i'm pretty sure D isn't the answer, but i'm not sure about the rest

Answer 1

A "watt" is a joule/sec so to combine seconds and hours is mismatched