Official套题51托福听力Lecture 1文本题目及答案解析【雷哥托福】2018-09-21 17:19:28 发布 来源：雷哥托福 阅读量:2967
1. What is the lecture mainly about?
A.A research study that compares wild and domesticated plants
B.Problems with a commonly held hypothesis about the origin of teosinte
C.Reasons why wild plants are usually unsuitable for agriculture
D.The process used to identify the ancestor of a modern crop
2.What evidence seemed to indicate that maize and teosinte are not related?
A.Young teosinte plants do not physically resemble young maize plants.
B.Preliminary DNA evidence indicated that teosinte was related to rice.
C.Maize and teosinte usually grow in significantly different climates.
D.Maize and teosinte have very different types of kernels.
3.Why does the professor discuss hybrids?
A.To explain how a geneticist confirmed that maize was widely grown 9,000 years ago
B.To indicate the earliest method used by geneticists to identify plant origins
C.To explain a method used to demonstrate a link between two plant species
D.To describe how geneticists distinguish between wild plants and domesticated plants
4.What was most researchers’ initial view of George Beadle’s theory about teosinte?
A.They accepted it but questioned the evidence cited.
B.They rejected it because of conflicting archaeological evidence.
C.They questioned it because it implies that ancient farmers were sophisticated plant breeders.
D.They questioned it because genetic research was viewed with skepticism at that time.
5.What did Beadle conclude about maize and teosinte?
A.Both plants lack particular genes that are common in most domesticated plants.
B.Both plants have particular genes that enable them to adapt to varying climates.
C.Only a small number of genes are responsible for the differences between the two plants.
D.The genetic composition of both plants is very similar to that of rice.
6.According to the professor, why was the discovery of a set of tools important?
A.It proved that teosinte was simultaneously domesticated in multiple locations.
B.It helped to confirm the period in which maize was first domesticated.
C.It suggested that maize required farming techniques that were more complex than experts had previously assumed.
D.It provided evidence that maize plants were used for more purposes than experts had previously assumed.