81. Health skin lies in ____.

1. a well-kept balance between two working processes
2. the two processes of breaking down skin cells
3. a fine balance in the number of cigarettes
4. the two steps of forming collagen

82. For the Japanese scientists, to test their idea is ____.

1. to verify the aging of human beings
2. to find out the mechanism of renewing skin
3. to prove the two processes of wrinkle formation
4. to confirm the hazards of smoking proven otherwise

83. The Japanese scientists tested their ideas using ____.

1. MMPs to form fresh collagen
2. cigarette smoke to contaminate skin cells
3. human fibroblasts to produce fresh collagen
4. non-smokers to be exposed to cigarette smoke

84. As inferred from Morita's results, smoking ____.

1. could stimulate the production of fresh collagen
2. is unlikely to promote the production of MMP
3. tends to cause skin to age prematurely
4. may cause collagen to die by 60%

85. Morita implies that his findings ____.

1. took less time than expected
2. were hard to accept in dermatology
3. were not exclusively based on the lab
4. need to be further verified in the human body

(Reference keys.)