A、They were expensive. B、No one believed them. C、They were unsuccessful. D、They were often not welcomed. C文章提到，第一代的绿色广告因为市场营销不佳，

Over the past decade, the environmental movement has exploded onto the minds of mainstream consumers, a fact not lost on marketers and advertisers. Green advertising started in the mid-1980s when issues of the environment muscled their way to the forefront of marketing. Advertisers saw the consumer desire for environmentally safe products and tried to meet the demand as quickly as pos sible.Not surprisingly, this first wave suffered from rough and poorly conceived marketing efforts. Many advertisers embraced a genuine concern for the environment. But consumers realized that some companies made false claims and exploited the movement using such nebulous terms as "envi ronmentally friendly" and "green". Consumers grew wary of environmental appeals, and advertis ers reacted by reducing its emphasis.Two legal guidelines paved the road to a second wave. In 1992 the Federal Trade Commission established guidelines for green marketing, followed shortly by state governments. California passed particularly stringent laws, setting definitions for terms like "ozone friendly," "biodegradable," and "recycled." According to the state’s court, "California seeks to guard against... potentially specious claims or ecological puffery about products with minimal en vironmental attributes." Texas, Massachusetts, Minnesota, Tennessee, Connecticut, and Washington soon followed the Golden State’s lead. The rigid regulations have left a number of advertisers con fused and frustrated, although some feel that environmental claims have already peaked and are on their way out. Some believe that we’ve now entered green advertising’s third wave, where environmental concerns are now part of the mainstream.
19. What were some early problems with the first wave of Green advertisements?
20. What do we know about consumers from the passage?
21. How did Green advertisements change after the first wave?