【题目】Teenagers should be cautious about the content on social networking sites, for their tastes and preferences ________ by what they see in the media.
A. shape B. were shaped
C. are shaped D. have shaped
在线课程【答案】C
【解析】考察被动语态。此处be shaped by短语意为“被…塑造，受…影响”，青少年应该十分小心社交网站上的内容，因为他们的品味和偏好总是受到他们在媒体上看到的东西的影响的。故选C。