单选题 When scientists are trying to understand a particular set of phenomena, they often make use of a "model." A model, in the scientists' sense, is a kind of analogy or mental image of the phenomena in terms of something we are familiar with. One example is the wave model of light. We cannot see light as if it were made up of waves because experiments on light indicate that it behaves in many respects as water waves do.
The purpose of a model is to give us a mental or visual picture -- something to hold onto -- when we cannot see what is actually happening. Models often give us a deeper understanding: the analogy to a known system (for instance, water waves in the above example) can suggest new experiments to perform and can provide ideas about what other related phenomena might occur.

单选题 Another example of a scientific model would be ______.
A. a map B. a paper airplane
C. an atom D. a light bulb

单选题 Why are models necessary?
A. They connect invisible phenomena to those we are familiar with.
B. Scientists could not experiment without them.
C. They give the scientist a sense of security.
D. They provide deeper insight into the workings of the human mind.

单选题 Models provide us with deeper understanding because ______.
A. they make us think about our universe
B. they were used to represent some other phenomena
C. they are more precise than theories
D. they indicate further direction and help us make predictions

单选题 An analogy is ______.
A. the study of the universe
B. a Comparison
C. the study of light waves
D. the result of scientific investigation