【正确答案】 D

【答案解析】[听力原文]
Some kinds of mental skills naturally decrease as people get older. Yet research seems to show that some training can improve such skills. A recently published study also appears to demonstrate that the good effects of training can last for many years after that training has ended.
Researchers at Johns Hopkins University in Maryland wanted to learn how long memory and thinking skills would last in older people who trained to keep them. The people were part of the ten-year re- search project. They were taught methods meant to improve their memory, thinking and ability to perform everyday tasks.
More than 2,800 volunteered for the study. Most studied when they were more than 70 years old. The volunteers took one of several short training classes meant to help them keep their mental abilities. One class trained participants in skills including how to remember word lists. Another group trained in reasoning. A third group received help with speed-of-processing—speed of receiving and understanding information. A fourth group—the control group did not get any training.
Earlier results had established that the training helped the participants for up to five years. Now, lead study writer George Rebok says, the research showed most of the training remained effective a till ten years later. Professor Rebok and his team found that the people trained in reasoning and speed-of-processing did better on tests than the control group. They are wondering whether those effects which endured over time would still be there ten years following the training, and in fact, that"s exactly what they found.

What can improve mental skills according to the research?

[解析] 短文开头提到，心智技能会随着人变老而自然减弱，然而研究似乎表明，通过一些训练可以增强这些(心智)技能。故选D。
①四个选项都是名词短语，听音时要留意录音有没提到。②A是随意捏造的选项，原文未提及；B和C中的memory和reasoning听力原文有提到，但是两者都属于mental skills(心智技能)训练的内容之一，而不是增强心智技能的手段。

【正确答案】 B

【答案解析】[听力原文]
What was the purpose of Johns Hopkins University"s research?

[解析] 短文提到，Johns Hopkins University的研究人员想知道受过记忆和思考技能训练的老年人能够保持这样的能力多久，B所述与此一致，故为答案。
①四个选项均是动词不定式短语，可知提问与做某事的目的有关。②帮助提高老人的记忆、思考能力并非研究的最终目的，研究目的是要看这种能力能保持多久，故排除A；培训主要是训练老人自己做某事的能力，而不是去“帮助”他们完成，故C也不对；D中的“寿命长短”录音并未提到，故也排除。

【正确答案】 B

【答案解析】[听力原文]
What does the term speed-of-processing refer to?

[解析] 短文提到speed-of-processing(处理速度)时，接着说了speed of receiving and understanding information(接受和理解信息的速度)，实际是对处理速度的解释，B可直接从原文听到，故为答案。
①四个选项均是以Speed of开头，可知提问与速度的概念相关。②A中的short training class、C中的memory and thinking skills和D中的reasoning均在录音里提及，但都是利用原文原词来进行干扰，与题干问及的speed-of-processing没有关系，均可排除。

【正确答案】 C

【答案解析】[听力原文]
What do we learn about the effects of most training?

[解析] 短文提到，研究表明大多数训练的效果在整整十年之后仍有效，听力结尾处再次强调了研究者想知道训练后的效果是否有十年那么长，而实际上，这正是他们研究所发现的。录音几处肯定，因此不难确定C正确。
①四个选项均是关于时效的表述，由此可推断提问与某事物的时效有关。②A和D原文均未提及，不难排除；原文有提到five years，但说的是早期的研究结果证明训练能帮助参与者维持心智技能长达5年，前面有up to限制，且也不是题目提及的大部分研究的结果，也可排除B。