导致的。故B正确。

2. 【答案】 A

【试题解析】推理题。根据文章第三段Generally, people believe that the hormone oxytocin is let out in our body in various social situations and和our body creates a large amount of it during positive social interactions (互动) such as falling in love or giving birth.第四段But in a previous experiment Professor Ryan found that the hormone is also let out in our body during negative social interactions such as envy在实验里Professor Ryan发现在消极的社会交往中，我们身体也释放出荷尔蒙，可知之前的实验告诉我们hormone oxytocin (荷尔蒙催生素)使用了另外一种形式来影响我们的行为。故A正确。

3. 【答案】 A

【试题解析】推理题。文章最后三行Professor Ryan thus concluded: "Our experiment proves that the hormone oxytocin can raise people's abilities to better distinguish different social interactions. And the behavior differences between men and women are caused by biological factors (因素) that are mainly hormonal."

可知，最近这次实验是想测试一下荷尔蒙催生素对辨认社交能力的效果，而结果证实了荷尔蒙催生素能提高人们的这种能力。

4. 【答案】 D

【试题解析】推理题。作者是通过讨论所做的不同的实验产生的不同的结果而展开，之前的实验结果和现在的实验结果的比对。产生新的结论。故D正确。

【长难句解析】

Further researches showed that in men the hormone oxytocin improves the ability to recognize competitive relationships, but in women it raises the ability to recognize friendship.

【翻译】进一步地研究显示在男性身上，荷尔蒙催生素能够提高辨认竞争性关系的能力，但是在女性身上，它能够提高辨认友谊的能力。

【分析】本句中的动词show后面有两个宾语从句in men the hormone oxytocin improves the ability to recognize competitive relationships, but in women it raises the ability to recognize friendship.使用了and连接。