题目内容：

    AIDS may be one of the most undesirable diseases in the world. Luckily, there is now hope for AIDS patients.

According to a recent paper published in the New England Journal of Medicine，Chinese scientists have successfully used CRISPR technology -a method of gene editing-to treat a patient with HIV. While it may not have cured the patient fully, it still represents a huge step forward in fighting the disease.

The patient was a 27-year-old Chinese man who was diagnosed with both AIDS and acute lymphoblastic leukemia (淋巴母细胞白血病), a type of blood cancer. Despite his bleak situation, doctors offered him a little hope: a bone marrow (骨髓) transplant to treat his cancer and an experimental treatment for his HIV. They used this chance to edit the DNA in bone marrow stem cells (干细胞) from a donor before transplanting the cells into the patient.

Specifically, the treatment involved using the gene-editing tool CRISPR-Cas9 to delete a gene known as CCR5, which encodes (给…编码) a protein that HIV uses to get inside human cells. Without the gene, HIV is unable to enter cells. Talking about the gene, lead scientist Deng Hongkui told CNN, “After being edited, the cells and the blood cells they produce have the ability to resist HIV infection.” Nineteen months after the treatment, the patients leukemia was in complete remission( 缓 解 ) and donor cells without CCR5 remained, according to the research paper.

Though the transplant didn't cure the man’s HIV, it still showed the effectiveness of gene-editing technology, as there was no indication of any unintended genetic changes-a major concern with past gene-editing treatment experiments. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security in the United States, who was not involved in the study, praised the treatment. “They did a very creative experiment, and it was safe,” he told Live Science. “It should be viewed as a success.”

Deng believes gene-editing technology could “bring a new dawn” to blood related diseases such as AIDS and sickle-cell anaemia ( 镰 状 细 胞 贫 血 ). “Thanks to this new technology, the goal of a functional cure for AIDS is getting closer and closer,” he said.

1.The underlined word “bleak” in Paragraph3 probably means “______”.

A.hopeless

B.unstable

C.embarrassing

D.unique

2.How did the treatment fight against HIV?

A.By identifying and killing HIV.

B.By changing the structure of HIV.

C.By preventing HIV entering cells.

D.By removing a protein HIV feeds on.

3.What is the result of the treatment?

A.Gene-edited cells are able to resist HIV infection.

B.The number of cells infected by HIV has decreased.

C.CCR5 and other genes in the patient's cells are changed.

D.Unintended genetic changes have taken place in the patient's cells.

4.What can we know about the experiment?

A.It pointed out the problems of gene treatment.

B.It provided a new way to cure AIDS patients fully.

C.It could offer a safe treatment for blood-related diseases.

D.It was the first example to use gene-editing tool to treat AIDS.