Archaeologists have many reasons to be interested in studying the remains of plants. Historically, humans have relied on plants as a source of everything frombuilding material to food and medicine. So, identifying plant remains at ancient human sites would help us gain insight into the way of life of a culture at a given point in time, but plants decay quickly, so it's rare to find intact specimens to examine. Even such seemingly sturdy stuff as seeds don't hold up over time, so what do we do? Fortunately, some plants leave behind microscopic traces of themselves that don't decay. Pollen and starch grains, for example, have been used in archaeological studies, as have what are called phytoliths. Phytoliths are very tiny, mineral deposits, almost like pieces of hard glass, that formin the cells or between cells of many kinds of plants. The minerals originate in the ground water that the plant absorbs through its roots. When the water runs through the plant's cells, the minerals are deposited. So, a phytolith is essentially a cast; 。。。。。余下托福听力真题原文省略！
Question 1 of 6
What is the main purpose of the lecture?
O A. To illustrate how phytoliths are beneficial to plants
O B. To demonstrate howphytoliths are used in scientific research
O C. To compare methods of analysis used in archaeological study
O D. To explain howmaize was first domesticated
Question 2 of 6
What is one way that phytoliths form?
O A. Grains become preserved between mineral layers in soil.
O B. Groundwater causes some of the plant tissue to decay.
O C. Minerals fromgroundwater collect in the cells of plants.
O D. Leaves of plants photosynthesize sunlight into minerals.