Which of the Following Events Best Exemplifies the Concept of Signaling

Which of the following events best exemplifies the concept of signaling?

A) A college student's parents, having learned that their child is short of money, send her a check for $1,000.
B) A new company making high quality bicycles at a reasonable price sends free bikes to reviewers working for bicycle magazines.
C) A grocery store maintains a policy of examining the driver's license of everyone who writes a personal check to purchase his groceries.
D) A university maintains a policy of considering for admission only those students who graduated among the top ten percent of their high school class.