71. Ruby's condition became serious when ____.

1. she was seven years old
2. her right leg began to drag
3. her right hand began to tremble
4. she began to work with a fender bender

72. A victim of Parkinson's, like Diane Ruby, ____.

1. may occur after a major stressful event
2. is usually diagnosed at age 40
3. is often diagnosed at age 50
4. appears over age 60

73. What is mysterious to scientists about Parkinson's?

1. The victim's hand tremors.
2. The lost control over muscles.
3. The production of dopamine in the brain.
4. The death of the cells in the substantia nigra.

74. According to the researchers at the Clinical Research Institute of Montreal, Parkinson's ____.

1. seems to be attributable to genetic factors
2. is caused by certain liver enzymes
3. cannot be genetically explained
4. mainly affects farmers

75. It can be learned from the passage that American researchers ____.

1. are interested in the relationship between Parkinson's and liver enzymes
2. disagree with the Canadian researchers on liver enzymes
3. confirmed what the Canadian researchers had discovered
4. plan to cooperate with the Canadian researchers

(Reference keys.)