练习：
1.Paragraph 2 _________.
2.Paragraph 3 _________.
3.Paragraph 5 _________.
4.Paragraph 6 _________.
A Reasons for Excluding Masks from the Self-protection List
B Effort to Stop Flu from Spreading
C When to Use Face Masks
D Guidelines on Mask Use
E Warnings from the CDC
F Danger of Infection through Germy Hands and Masks
5.The scientists are trying to find out if masks may or may not _________.
6.The CDC is afraid that the public may _________.
7.The public will not know the answer about masks until scientists _________.
8.We can infer from the passage that the US authorities _________.
A overuse face masks
B deal with the mask problem seriously
C rub their faces and noses in the subway
D protest against the mask guidelines
E help protect people from being attacked by a flu
F announce the results of their mask research