86. Which of the following is the best title for this passage?

1. Medical Breakthroughs of the 19th Century.
2. The Fight against Bacterial Infections.
3. The Power and Promise of Vaccines.
4. How the Human Immune System Works.

87. The Chinese and the Turks are examples of cultures that ____.

1. identified viruses by name
2. employed early forms of vaccination
3. were almost eliminated by viral diseases
4. mistook bacteria for viruses

87. Viruses cause all of the following EXCEPT ____.

1. tuberculosis
2. cowpox
3. rabies
4. smallpox

89. According to the passage, bacteria are like viruses in that they ____.

1. cannot reproduce on their own
2. have been virtually eradicated
3. played a major role in the discovery of vaccines
4. are parasitic

90. The word "signature" (Line 7, Para. 3) most nearly means ____.

1. dangerous
2. official
3. identifying
4. invisible

(Reference keys.)