Marketing question.please help.10 points?

[pure shooter]

Abercrombie & Fitch, a hip clothing retailer, includes a "Share it!" button on its website. This button encourages an Abercrombie customer to post a link to a product page (perhaps showing a new style of jeans) on Facebook or Twitter. Abercrombie & Fitch hopes that the customer's friends (who are probably very much like current customers) will click the link, visit the page, and make purchases. This is an example of a ______ growth strategy.

a.product development
b.market development
c.market penetration

[norcekri]

This is market development. They've already penetrated, and are now working to develop a larger market share.

How is it that you didn't figure this out from the definitions in your book?