vì sao khi nhiễm bệnh lần đầu các bác sĩ chỉ xét nghiệm thấy sự có mặt của kháng thể sau 6-7 ngày, nhưng khi nhiễm bệnh lần 2 thì kháng thể xuất hiện sớm hơn và số lượng lại nhiều hơn?

Các câu hỏi liên quan

1. I wish you ………stop making that noise. It’s bothering me. A. would B. are going to C. will D. can 2. This residential area used ………a huge landfill. A. being B. been C. was D. to be 3. She ……… to wear dresses, but now she does most of the time. A. used B. didn’t use C. was used D. wasn’t used 4. They are running a ………program to help these kids read and write better. A. social skills B. cognitive skills C. literacy D. stress-coping 5. I ………dinner when my parents came home. A. eat B. had eaten C. am eating D. ate 6. It was ……….of him to show up at the meeting in jeans. A. certain B. annoyed C. useful D. unprofessional 7. She is astonished ……… the puppet has grown so much in 2 months. A. when B. if C. that D. for 8. It ………that five people had been injured in the car crash. A. reported B. has reported C. was reported D. reports 9. Eating from ………. is a popular habit of people in big cities in Vietnam. A. street vendors B. libraries C. canteens D. shops 10. It is considered good behaviours to give away to ………people in a bus or train. A. senior B. young C. depressed D. impolite 11. Like a local, you should take an afternoon …….. ride through the bustling streets of Ha Noi’s Old Quarter. A. architectural B. geological C. complex D. rickshaw 12. Hai Van ………..is 2.8 km long. A. elevated walkway B. flyover C underpass D. tunnel 13. The children in my home village used to go ………, even in winter. Now they all have shoes. A. on foot B. bare-footed C. playing around D. by bike 14. The Imperial Citadel of Thang Long is a ……… that consists of royal palaces and monuments. A. setting B. complex C. structure D. measure 15. She suggests ……… to protect the environment. A. recycling B. recycle C. recycled D. to recycle 16. I would suggest that you ……… your doctor about this. A. said B. says C. should say D. to say 17. Hue’s most outstanding attractions are the emperors’ ………. . A. tombs B. graves C. caverns D. cathedrals 18. Our environment has been ……….polluted. A. gradual B. gradually C. gradualism D. gradualness 19. She lived in a(n) ……… family, so she didn’t have much privacy. A. rich B. poor C. nuclear D. extended 20. The hotel is beautifully ……… in a quiet spot near the river. A. landed B. lied C. stood D. situated