题目内容：

One step too far

Scientists have been trying to figure out how to alter the genes of humans for many years now, and it looks like they've finally cracked (破解) the code. But while this may seem like a great step forward in science, some also believe that it's one step back when it comes to ethics.

In August, a group of scientists from the US and South Korea worked together to successfully edit a human embryo and remove a genetic mutation (突变) that would have led to heart disease, reported The Guardian.

This was achieved with the help of CRISPR, a gene-editing tool that allows scientists to “cut and paste” human DNA.

Although this was the first example of an embryo's genes being changed successfully, the benefits of gene editing have already been tested in living patients.

In 2015, a five-month-old girl from the UK was saved after doctors used edited cells to fight off her cancer. As of today, she's alive and well.

And in the US last year, scientists managed to remove HIV cells from several patients by editing the genes inside their bodies.

Some people hope that in the future, diseases or birth detects could simply be “edited out”. However, others believe this could lead to so-called designer babies, giving parents the option to choose everything from eye color to intelligence.

“You could find wealthy parents buying the latest ‘upgrades’ for their children, leading to even greater inequality than we already live with,” Marcy Darnovsky, director of the San Francisco Center for Genetics, told BBC News.

In spite of these ethical concerns, experts say it’s not possible to create the “perfect” human being. Despite the progress scientists have made, we don’t understand human genes enough to give all unborn child great brainpower or amazing singing abilities.

“Right now, we know nothing about genetic enhancement,” Hank Greely, a director of sciences at Stanford University, US, told The New York Times. “We’re never going to be able to say, honestly, ‘This embryo looks like it would score high on the two-part SAT.’”

So it looks like if we want good exam results, or to impress people with our piano skills, we’ll have to stick with the old fashioned method of plain hard work — at least for now.

1.The underlined word “alter” in Paragraph 1 probably means ______.

A.record

B.change

C.remove

D.increase

2.Why do some people consider human gene editing a step backwards？ ______

A.They don't think it is an effective way to light diseases.

B.They are concerned that it could lead to genetic mutations.

C.They think it could lead to designer babies and increased inequality.

D.They worry that it could make parents abandon children with birth defects.

3.What was the first successful example of human embryo gene editing？ ______

A.A genetic mutation related to heart disease was removed by scientists

B.A newborn baby with cancer was saved by edited cells.

C.HIV cells were removed from patients’ bodies.

D.Some birth defects were simply edited out.

4.What can we conclude from the text？ ______

A.Gene editing is regarded as the perfect way to treat birth defects.

B.There is still a long way to go to fully understand human genes.

C.Gene editing could help enhance human intelligence in the near future.

D.Scientists are pessimistic about the future of gene editing.