According to the passage, Dr. Casey probably agrees that teens ______.

参考解析：

细节理解题。由“Dr. Casey”定位到文章第四段第四句话“The researchers discovered that the number of risks teens took more than doubled when their friends were watching, compared with when they played alone.”可知，研究者发现，相比于青少年独自玩游戏，在有朋友观看的时候，青少年会更加敢于冒险，所以C项正确；根据第四段第三句“In a recent study, teen volunteers played a video driving game, either alone or with friends watching”可知只是陈述研究的细节，无法体现青少年喜欢和朋友一起玩开车游戏，所以A项错误；根据第四段第一句“teens are very quick and accurate in making decisions on their own and in situations where they have time to think.”可知，青少年在独自一人或者在有时间思考的情况下做决定更快更精确，但是无法体现青少年喜欢有时间思考的场合，所以B、D项错误。故选C。