2. Passage Twenty-SevenOut of all the students who enroll in a massive open online course (MOOC)， only about 5 percent complete the course and receive a certificate of accomplishment.This statistic is often cited as evidence that MOOCs are fatally flawed (有缺陷的)and offer little educational value to most students.Yet more than 80 percent of students who fill out a post-course survey say they met their primary objective.How do we look at these two facts? We’re used to focusing on completion rates in higher education， but they’re not the only—or even the most meaningful—indicator of engagement in open online courses.With no cost to enroll， no punishment for dropping out， and little reward for actually earning a certificate， MOOCs are fundamentally different from traditional classes—and students use them in fundamentally different ways.Data from more than 1.8 million students enrolled in 36 MOOCs offered by the University of Pennsylvania show that students treat MOOCs like a buffet (自助餐)， sampling the material according to their interests and career goals.Some are curious about the subject matter and just watch one or two video lectures; others use the discussion forums to connect with their intellectual peers around the world.Of all enrolled students， nearly 60 percent watch at least one video， complete at least one assignment， or post at least once in a forum.So focusing on the tiny fraction of students who complete a MOOC is misguided.The more important number is the 60 percent engagement rate.Students may not finish a MOOC with a certificate of accomplishment， but the courses nonetheless meet the educational goals of millions.In Para.2， the author stresses ().

31. Questions 31 to 35 are based on the following passage.The United States is facing a housing crisis: Affordable housing is inadequate， while luxury homes abound (充裕)， and homelessness remains a persistent problem.Despite this， popular culture and the housing industry market happiness as living with both more space and more amenities (便利设施).Big houses are advertized as a reward for hard work and diligence， turning housing from a basic necessity into a luxury.This is reflected in our homes.The average single-family home built in the United States before 1970 was less than 1，500 square feet in size.By 2016， the average size of a new， single-family home was 2，422 square feet.What’s more， homes built in the 2000s were more likely than earlier models to have more of all types of spaces: bedrooms， bathrooms， living rooms， dining rooms， recreation rooms and garages.There are consequences of living big.As middle-class houses have grown larger， two things have happened.First， large houses take time to maintain， so cleaners and other low-wage service workers are required to keep these houses in order.Second， once-public spaces， where people from diverse backgrounds used to come together， have increasingly become privatized， leading to a reduction in the number of public facilities available to all， and a reduced quality of life for many.Take swimming pools.While in 1950， only 2，500 U.S.families owned pools， by 1999 this number was 4 million.At the same time， public municipal pools were often closed， leaving low-income people nowhere to swim.The trend for bigger housing thus poses ethical questions.Should Americans accept a system in which the middle and upper classes enjoy a luxurious lifestyle， using the low-wage labor of others? Are we willing to accept a system in which an increase in amenities purchased by the affluent means a reduction in amenities for the poor?I believe neither is acceptable.We must change the way we think: living well does not need to mean having more private spaces; instead， it could mean having more public spaces.A better goal than building bigger houses for some is to create more publicly accessible spaces and amenities for all.What are big houses promoted to be in the United States?

20.Although Anne is happy with her success she wonders ()will happen to her private life.

19.Wouldn＇t you rather your child ()to bed early?

18.Some diseases are ()by certain water animals.

17.This kind of glasses manufactured by experienced craftsmen ()comfortably.

16.The sale usually takes place outside the house， with the audience ()on benches， chairs or boxes.

15.Corn originated in the New World and thus was not known in Europe until Columbus found it ()in Cuba.

14.The hopes， goals， fears and desires widely ()between men and women， between the rich and the poor.

13.I don＇t mind ()the decision as long as it is not too late.

12.Niagara Falls is a great tourist ()drawing millions of visitors every year.