Which of These Is the Best Example of the Concept

Which of these is the best example of the concept of cultural lag?

A) a lack of clear law governing the rights of all parties involved in artificial insemination and other forms of reproductive technology
B) the use of radar to determine and document the speed of drivers on a major highway
C) an increase in the use of Facebook among people over age 50 to find former high school and college classmates
D) a lack of electronic versions of older novels, biographies, and other published works