[解析]
(1)C.细节理解题。根据第一段But前后两句话的描述,巧克力是我们喜欢的一些甜品的主要部分,但它又不是一种健康食品,因此,我们要适度享用它。in moderation适度地。故选C.
(2)D.细节理解题。根据第三段对研究结果的表述The scientists found improvements in general cognition,attention,processing speed and working memory.可知,科学家们发现了巧克力能使人们在一般认知、注意力、处理速度和记忆方面得到改善。故D项He understands what the teacher says faster.(他能更快的理解老师讲的内容)符合题意,故选D.
(3)B.细节理解题。根据第四段 The researchers also found that eating chocolate daily (over periods ranging from five days to three months) produced noticeable long﹣term improvements in cognition.Older adults,whose memories were already declining,saw an especially significant improvement.(研究人员还发现,每天吃巧克力(从五天到三个月不等)能显著提高认知能力。老年人的记忆力已经在下降,他们的记忆力有了显著的提高。)可知,每天吃巧克力对认知能力有明显的长期改善。再根据第一段But it's not a health food可知,巧克力不是健康食品,所以只适合做零食,故选B.
(4)A.主旨大意题。科学研究发现吃巧克力对身体有很大的好处,尤其是可以提高人们的认知表现。但是它高糖低营养,因此选A,巧克力是一种有益(beneficial )但不健康的(unhealthy)食品。故选A.