________ is an unpaid form of promotion. It can have positive and negative effects on the recipient. For example, when you log onto CNN and read that four auto assembly-line plants are closing, it is not good news for our economy. However, on the same site, if you read about a company's water recycling effort targeted toward good stream management, you are usually impressed.a) Product placementb) Viral marketingc) Publicityd) Sales promotion