Around 120 years ago, Ebbinghaus began his study of memory. He (1) on studying how quickly the human mind can remember (2) . One result of his research is known as the total time hypothesis (假设), which simply means the amount you learn (3) on the time you spend trying to learn it. This can be taken as our first rule of learning.
Although it is usually true that studying for four hours is better than studying for one, there is still the question of how we should use the four hours. For example, is it better to study for four hours (4) or to study for one hour a day for four days in a (5) The answer, as you may have (6) , is that it is better to spread out the study times. This (7) through which we can learn more (8) by dividing our practice time, is known as the distribution of practice effect. Thus, (9) .
But we’re not finished yet. We haven’t considered how we should study over very short
Thousands of years (21) humans began the process of domesticating the dog and shaping what "being a dog" really means. Through careful selection and breeding, an astonishing variety of dog breeds (22) been created. Desirable traits have been selected for in various breeds that are of a benefit (23) humans. There are some traits, however, that quickly become undesirable when expressed too frequently. Barking is a(an) (24) of a natural behavior that is encouraged in terms of guarding behavior, but becomes a problem when the behavior is produced in excess. A recent health insurance investigation revealed (25) the sound of a continually barking dog was cited as the most disruptive and stress inducing (26) for humans.
Barking, in addition to whining, howling and growling, is a dog’s (27) means of communication. Barking is characterized by a series of short, sharp sounds, that tend to vary (28) <
A. would
B. must
C. can
D. needs
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