Question 18 is based on the passage you have just heard.

     (16) Scientists understand how twins are born. Now, though, they are trying to explain how being half of a biological pair influences a twin’s identity. They want to know why many identical twins make similar choices even when they don’t live near each other. For example, Jim Springer and Jim Louis are identical twins. They were separated when they were only four months old. (17) The two Jims grew up in different families and did not meet for 39 years. When they finally met, they discovered some surprising similarities between them. Both men were married twice.Their first wives were named Linda, and their second wives were both named Betty. Both twins named their first sons James Allan. Scientists want to know what influences our personality. (18) They study pairs of identical twins who grew up in different surroundings, like Jim Springer and Jim Louis. These twins help scientists understand the connection between environment and biology. Researchers at the University of Minnesota studied 350 sets of identical twins who did not grow up together. They discovered many similarities in their personalities. Scientists believe that personality characteristics such as friendliness, shyness and fears are not a result of environment. These characteristics are probably inherited. Scientists continue to study identical twins because they are uncertain about them and have many questions. For example, they want know “Can twins really communicate without speaking?” “Can one twin really feel another twin’s pain?” Perhaps with more research scientists will find the answers.

(18). Why are scientists interested in studying identical twins raised in different families?

解析：A。本题目为细节题。问题为：为什么科学家对研究不同家庭中的同卵双胞胎感兴趣？根据原文“They study pairs of identical twins who grew up in different surroundings, like Jim Springer and Jim Louis. These twins help scientists understand the connection between environment and biology.”可知科学家研究生长在不同环境的双胞胎，这能帮助他们理解环境和生物之间的关系，故正确答案选A。