Sergio Pellis 出现在E段的开头：Earlier this year, Sergio Pellis of Lethbridge University, Canada, reported that there is a strong positive link between brain size and playfulness among mammals in general. Comparing measurements for fifteen orders of mammal, he and his team found larger brains (for a given body size) are linked to greater playfulness. The converse was also found to be true.
Sergio Pellis reported that there is a strong positive link between brain size and playfulness among mammals in general(可删).
由此，回到选项中，进行对应，唯有：D. There is a tendency for mammals with smaller brains to play less. (smaller brains 与play less就是对称正比的诠释)。选项A. There is a link between a specific substance in the brain and playing. 是干扰项，因为这里的link between.... and ....之间的名词所指不同。