What is considered the most primitive true animal?
A) Porifera
B) Cnidaria
C) Annelida
D) Mollusca
A
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Maintaining sustainable human exploitation of ecosystem capital will be increasingly difficult because of
A) over-reliance on grains and other plants as a significant portion of the human diet. B) expanding number of viral and bacterial human diseases. C) growing pressure from human population on Earth. D) changing temperature and rainfall patterns.
Which of the following bonds is the most polar?
A) C-H B) C-N C) C-O D) C-F
How many electrons are associated with a single bond?
A) 1 B) 2 C) 4 D) 6
In toxicology studies, LD50 can be best described as the dose ________
A) at which 50% of an exposed population develops a chronic effect from the toxicant B) at which 50% of an exposed population develops disease C) at which more than 50% of the population dies as a result of the toxicant development D) at which 50% of an exposed population is killed or displays a specific symptom E) at which at least 50% of the exposed population is not affected by the toxicant