[解析]
(1)C.细节理解题。根据第一段第一句It is often said that you can't have too many friends. (人们常说,朋友越多越好)。可知,朋友愈多愈好。故选C。
(2)A.细节理解题。根据第二段They were also given free mobile phones and agreed that researchers could use their bills to work out who they called,when and for how long. (他们还获得了免费的手机,并同意研究人员可以使用他们的账单来确定他们打电话的对象、时间和时长。)可知,研究的方法之一是核实志愿者的通话记录。故选A。
(3)D.细节理解题。根据第三段As the volunteers' lives changed,including the number of best friends,remained almost the same (随着志愿者生活的改变,这个总体模式,包括最好的朋友的数量,几乎保持不变)和第四段He added that this finding suggest even with the coming of modern technology we are only capable of forming a limited number of true friendships.(他补充说,这一发现表明,即使现代科技的到来,我们也只能形成有限数量的真正的友谊。)可知,即使随着现代科技的到来,一个人结识的好朋友的数目仍然是有限的,一个人最好朋友的数量变化不大。故选D。
(4)B.推理判断题。由最后一段Our results are likely to reflect limitations in the ability of humans to keep emotionally close friendships both because of limited time and because the emotional capital that individuals can allocate between family members and friends is limited.(我们的研究结果很可能反映了人类保持亲密情感友谊的能力有限,这既是由于时间有限,也是因为个人可以在家庭成员和朋友之间分配的情感资本有限。)由此可知,最后一段的作用是为了解释研究结果的原因所在。故选B。