Answer: Option (D) is correct.
Step-by-step explanation:
An economic signal is a type of information on a particular good, product or activity which helps people in making economically correct decisions.
All the options are showing economic signal in some way:
(a) There is a fall in the demand for floppy disks and CDs which shows that there is a trend change.
(b) High unemployment rate in U.S will lead to a decision to employ more number of people.
(c) This increases the demand for houses.
(d) There is a indication about the future prices of toilet paper that it will not change much in the future.