tailieunhanh - Đề KTCL ôn thi THPT Quốc gia năm 2017 môn tiếng Anh - THPT Liễn Sơn - Đề số 07

Đề KTCL ôn thi THPT Quốc gia năm 2017 môn tiếng Anh - THPT Liễn Sơn - Đề số 07 gồm 50 câu hỏi trắc nghiệm, hi vọng sẽ giúp quý thầy cô thuận tiện hơn trong việc ra đề và các em học sinh ôn thi thật hiệu quả. Mời quý thầy cô và các em cùng tham khảo. | Scientist have believed that they have made a (26)_ breakthrough in fighting HIV- they have shown what happens when an infection-fighting antibody attacks a gap in HIV’s considerable defenses. Finding a vaccine against HIV has been very difficult because the proteins on the surface of the virus are continually mutating, but they have shown an antibody, called b12, attacking a weak spot of the virus where the protein is (27)_. The virus is able to mutate rapidly to avoid detection by the immune system, and is also covered in sugary molecules which block access by antibodies. However, certain parts of the virus must remain (28)_ unchanged so that it can catch hold of and enter human cells. One protein that sticks out from the surface of the virus and binds to receptors on host cells is one such region, which makes it a target for vaccine development. Previous analyses of the bleeding of people that have been able to keep HIV from developing into AIDS for long periods of time (29)_ revealed a rare group of antibodies- including b12- that seem to fight HIV with some degree of structure. The latest study showed how the antibody and the protein interact. Scientists hope that revealing the (30)_ of this bond in such precise detail will provide clues about how best to attack.