单选题______ from space, our earth, with water covering 70% of its surface, appears as a "blue planet". A. See B. Seeing C. Seen D. To be seen

单选题Ever since Picasso's paintings were on exhibition, there ______ large crowds at the museum very day. A. is B. have been C. has been D. are being

单选题My typist has not returned my paper yet, but she promised ______ by tomorrow.

单选题Jack: Hey, how are you, Susie? Gee, we haven't seen each other in... It must be close to three years! Susie:______ Jack: OK.

单选题He has never visited the town ______ he was born. A. where B. which C. on which D. that

单选题Millions of Americans flock to their drugstores to buy vitamins and minerals, ______ that these pills can help to prevent serious illnesses.

单选题中国著名的芭蕾舞表演艺术家( )被称为中国的第一只“白天鹅”。

单选题The winter vacation ______ over, he got down to his work again. A. was B. were C. had been D. being

单选题Dow Jones News is important because ______.

单选题All things ______, the planned trip will have to be called off. A. considered B. be considered C. considering D. having considered

单选题A: This is one of a pair, isn't it? B: Yes, madam. A. Well, can I see the other one, please? B: ______ A. Certainly, madam, here it is. B. Fancy meeting you here. C. That's right, but you are late. D. How can I help you?

单选题______ in the United States, St. Louis has now become the 24th largest city. A. Being the fourth biggest city B. It was once the fourth biggest city C. Once the fourth biggest city D. The fourth biggest city it was

单选题Passage Four 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Cathleen: Let's take a coffee break, shall we? Yolanda: ______but I can't. A. We shall B. Yes, let's C. You will D. I wish I could

单选题Patient: I strained my back the other day working in the garden. Doctor: ______ A. Why so careless? B. Well, you need an X-ray. C. When did it start? D. Well, go and stay in bed.

单选题At the end of the discussion, he Usummed up/U and added a few points.

单选题The two passengers ______ the crash and were given emergency treatment at the scene of the crash.

单选题Speaker A: I'm so worried about this job interview. speaker B: Don't worry. ______.