IELTS Reading Sentence Completion

Hydroelectric plants harness energy by passing flowing water through a turbine. The water turbine rotation is delivered to a generator, which generates electricity. The quantity of electricity that can be produced at a hydroelectric plant relies upon two variables. These variables are (1) the vertical distance that the water falls, called the “head”, and (2) the flow rate, calculated as volume over time. The amount of electricity that is produced is thus proportional to the head product and the flow rate. Until only recently people believed almost universally that hydroelectric power was an environmentally safe and clean means of generating electricity. Hydroelectric stations do not release any of the usual atmospheric pollutants emitted by power plants fuelled by fossil fuels so they do not add to global warming or acid rain. Nevertheless, recent studies of the larger reservoirs formed behind dams have implied that decomposing, flooded vegetation could give off greenhouse gases equal to those from other electricity sources.

For the first question, “produce” also means “harness”. If you read through the passage you find that the first line contains the information “Hydroelectric plants harness energy by passing flowing water through a turbine.” So the answer is “flowing water”.

For the second question,  you find in the passage that the second  line contains the information “The water turbine rotation is delivered to a generator, which generates electricity.” So the answer is “turbine rotation”.

For the third and fourth questions, the fifth line of the passage contains the information “The amount of electricity that is produced is thus proportional to the head product and the flow rate.” So the answers are “head product” and “flow rate”

For the fifth question, the seventh line of the passage has the information “they do not add to global warming”. So the answer is “global warming”

Dendrochronologists, scientists who study the growth of rings in trees, have successfully constructed long tree-ring records by overlapping the patterns of wide and narrow rings in successively older timber specimens. There are now a dozen or so chronologies in the world that date back more than 5,000 years. These records, normally constructed in a restricted area, using a single species of tree, are year-by-year records of how the trees reacted to their growth conditions — an environmental history from the trees’ point of view. The study provides a year-by-year estimate of temperatures, together with the dates of some major volcanoes. It is a nice clean story — volcanoes load the atmosphere with dust and aerosol and reflect back sunlight, cooling the earth’s surface. This cooling leads to variations in the density of growth rings in northern conifers. The wood hewn from trees and preserved through the centuries is slowly beginning to yield at least circumstantial evidence of important historical events.

1. What are people who study the growth of rings in trees called as?
2. How many species of trees are used for creating a record?
3. What dates does the study the growth of rings in trees provide?
4. How do volcanoes cause variations in the density of growth rings in northern conifers?
5. What serves as a record for important historical events?

1. Dendrochronologists
2. One
3. Major volcanoes
4. By cooling earth’s surface
5. Wood hewn and preserved

For the first question, we find the answer in the first line of the passage which says “Dendrochronologists, scientists who study the growth of rings in trees”. So the answer is “Dendrochronologists”.

For the second question, we find the answer in the third line of the passage which says “These records, normally constructed in a restricted area, using a single species of tree”. Single means one. So the answer is “one”.  

For the third question, we find the answer in the fourth line of the passage which says “The study provides a year-by-year estimate of temperatures, together with the dates of some major volcanoes”. So the answer is “major volcanoes”

For the fourth question, we find the answer in the fifth and sixth line which say “It is a nice clean story — volcanoes load the atmosphere with dust and aerosol and reflect back sunlight, cooling the earth’s surface. This cooling leads to variations in the density of growth rings in northern conifers.” So the answer is “By cooling earth’s surface”

For the fifth question, we find the answer in the last line of the passage which says “The wood hewn from trees and preserved through the centuries is slowly beginning to yield at least circumstantial evidence of important historical events.” So the answer is “ wood hewn and preserved”.

NOTE: Follow the instruction which says “NOT MORE THAN FOUR WORDS”. Frame your answers accordingly.