单选题 Science is an enterprise concerned with gaining information about causality, or the relationship between cause and effect. A simple example of a cause is the movement of a paddle as it strikes a ping-pong ball; the effect is the movement of the ball through the air. In psychology and other sciences, the word "cause" is often replaced by the term "independent variable". This term implies that the experimenter is often "free" to vary the independent variable as he or she desires (for example, the experimenter can control the speed of the paddle as it strikes the ball). The term "dependent variable" replaces the word "effect", and this term is used because the effect depends on some characteristic of the independent variable (the flight of the ball depends on the speed of the paddle). The conventions of science demand that both the independent and dependent variables be observable events, as is the case in the ping-pong example. In the case of biorhythm theory, the independent variable is the number of days that have elapsed between a person's date of birth and some test day. The dependent variable is the person's level of performance on some specified task on the test day. Notice that although the experimenter is not free to choose a birthday for a given individual, persons with different dates of birth can be tested on the same day, or a single subject can be tested on several different days.
In order to predict the relationship between independent and dependent variables, many scientific theories make use of what are called intervening variables. Intervening variables are purely theoretical concepts that cannot be observed directly. To predict the flight of a ping-pong ball, Newtonian physics relies on a number of intervening variables; including force, mass, air resistance, and gravity. You can probably anticipate that the intervening variables of biorhythm theory are the three bodily cycles with their specified time periods. It should be emphasized that not all psychological theories include intervening variables, and some psychologists object to their use precisely because they are not directly observable.
The final major component of a scientific theory is its syntax, or the rules and definitions that state how the independent and dependent variables are to be measured, and that specify the relationships among independent variables, intervening variables, and dependent variables. It is the syntax of biorhythm theory that describes how to use a person's birthday to calculate the current status of the three cycles. The syntax also relates the cycles to the dependent variable, performance, by stating that positive cycles should cause high levels of performance whereas low or critical cycles should cause low performance levels. To summarize, the components of a scientific theory can be divided into four major categories: independent variables, dependent variables, intervening variables, and syntax.

单选题 Based on the passage, causality may have the meaning that ______.
A. cause and effect can be independent of each other
B. there is hardly anything that happens without a cause
C. dependent and independent variables affect each other
D. cause and effect may vary respectively in most events

单选题 According to biorhythm theory, ______.
A. one's behavior can be predicted by knowing his or her birthday
B. nobody can choose his or her date of birth as he or she wishes
C. an individual's performance is irrelevant to his or her birthday
D. a person's level of performance varies according to the test date

单选题 Many theories for predicting the relationship between cause and effect ______.
A. testify their complete conformity with general scientific principles
B. justify the identity of dependent, independent, and intervening variables
C. specify the time periods of bodily cycles in terms of psychological tests
D. verify their prediction by variables inconsistent with conventions of science

单选题 The example of the ping-pong ball is used to ______.
A. indicate a hard nut to crack in physics
B. predict variables in a person's performance
C. prove a common feature most theories have
D. show the negligibility of intervening variables

单选题 The word "syntax" used in the last paragraph refers to the ______.
A. rules used for ordering and connecting words in a sentence
B. principles defining the connections among different variables
C. definitions describing the impact of biorhythm on one's behavior
D. criteria measuring a person's performance levels with biorhythm