1. are small sacs where oxygen and carbon dioxide are transferred.
A. capillaries
B. lungs
C. alveoli
D. all of the above
2.Animals' quick responses to the environment are due to excitable cells called nerve cells, or neurons.
true or false
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question 1: c. alveoli

question2 : true

Explanation:

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each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.