题目内容：

    The year 2018 will mark the 100h anniversary of the deadliest influenza outbreak in history. It is estimated that the influenza pandemic (瘟疫) of 1918 killed more than 50 million people around the world. Other estimates go much higher. Because of a lack of medical record-keeping, we may never know the exact number.

The influenza was a fast killer. Some victims died within hours of their first symptoms. Others died after a few days. “Their lungs filled with liquid and they choked to death.” The 1918 flu pandemic was also different from other outbreaks. It struck many young. healthy people. Viruses usually affect sick or old people.

Although modern medicine effectively controls many diseases, influenza remains difficult to protect against. The World Health Organization estimates that every year influenza kills 250,000 to 500,000 people around the world. Each year, medical scientists develop flu vaccines (疫苗) which offer immunity (免疫) from some influenza viruses. But they can only guess which form of the virus will spread.

Health officials remain concerned about another flu pandemic. New forms of the flu virus appear regularly. One example was the “swine flu” or H1N1 outbreak in 2009. Anthony Faucal, Director of the National Institute of Infectious Diseases in the United States says that virus caused a true pandemic.

To stop the next pandemic, scientists are now researching how to create a universal influenza vaccine. In October 2017, Vanderbilt University Medical Center in the U. S. announced the Universal Influenza Vaccine Initiative. The university said researchers are leading an international effort to develop a universal influenza vaccine that will protect everyone against all forms of the flu anywhere in the world. The university added that researchers will begin tests in early 2018. The Human Vaccines Project, a public-private partnership, is funding the project. However, until a universal influenza vaccine is available, today’s seasonal flu vaccine remains important.

1.Why is influenza difficult to protect against?

A.It spreads too rapidly.

B.It is quite easy to catch.

C.No vaccine is available.

D.It's hard to judge the form of virus.

2.What does the author want to tell by mentioning H1N1 in 2009?

A.New forms of flu virus keeps appearing.

B.It was the most serious in recent years.

C.It was caused by the same flu virus of 1918.

D.The H1N1 virus was deadly as well.

3.What can we learn about the universal influenza vaccine?

A.The development is quite costly.

B.It will be used all over the world.

C.It can protect against all forms of flu.

D.It will soon come into use in 2019.