一个信号不能在时域或频域上都是有限的。

A．they have less time to devote to school assignments

B．they get too tired from work to study

C．they view school more rewarding

D．they take drugs and use alcohol more often than non-working students

Although the causes of cancer______, we do not have any practical way to prevent it.

A．are being uncovered

B．have been uncovering

C．are uncovering

D．have uncovered

A、different definitions and explanations

B、similar definitions and explanations

C、causes and effects

D、advantages and disadvantages

A、check whether what one said is true

B、ask why questions several times

C、ask wh- questions

D、see what we can do about it

A、ignoring details

B、over-generalizing

C、imposing consistency

D、preconnecting causes and effects

Please complete the text summary with appropriate words or expressions according to your understanding: There are _________ and _______ ways by which one can measure the ________ of employment on ___________. We compared the grades of students working a lot with those working much less or not at all. We also _________ workers with non-workers __________commitment to education. Additionally, we followed students over time as they increased or decreased their work hours, and we _______ of different employment patterns on school ___________. We uncovered numerous explanations for these negative effects: Working students have less time to _______ school assignments, get too tired from work to study, view school less rewarding, and increase alcohol and drug use because they have more spare money. To summarize, working 20 hours or more weekly can ___________ decreased school performance and increased drug and alcohol use. If students want to be successful in school, they should ________ that early employment builds character and __________ work no more than 10 hours per week.

A、details

B、explanations

C、instructions

D、action and reaction