属于天然高分子囊材的是
A. 聚乳酸
B. 明胶
C. 乙基纤维素
D. 羧甲基纤维素
E. 枸橼酸
属于生物可降解性合成高分子囊材的是
A. 聚乳酸
B. 明胶
C. 乙基纤维素
D. 羧甲基纤维素
E. 枸橼酸
Chomsky defines "competence" as the ideal users______ of the rules of his language.
A. instinct
B. knowledge
C. performance
D. realization
According to Dr William Cohn, the artificial heart______.
A. mimics the action of the heart found in humans
B. provides the blood flow of a natural human heart
C. produces pulses by a continuous-pump mechanism
D. uses a small spinning turbine to keep blood flowing at a steady rate
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