The beginning of the Cambrian period marks an important event in animal evolution — the appearance of organisms with ________.

A) wings
B) cells
C) hard parts
D) vertebrae
E) none of the above


Ans: C) hard parts

Environmental & Atmospheric Sciences

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A) involves using the governing equations. B) applies equations only once. C) is not run on a computer. D) is used only in short-term forecasts.

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North America is NOT a region that is affected by desertification

Indicate whether the statement is true or false

Environmental & Atmospheric Sciences

Describe the eolian processes of deflation and abrasion

What will be an ideal response?

Environmental & Atmospheric Sciences

Which of the following statements about underground contaminants is false?

a. Degradable organic wastes do not decompose as rapidly underground as on the surface. b. There is little dissolved oxygen to aid in degradation of wastes. c. Waste products are diluted and dispersed quickly in underground aquifers. d. It can take hundreds to thousands of years for contaminated groundwater to cleanse itself of degradable wastes. e. In some coastal areas, groundwater has been contaminated by saltwater intrusion.

Environmental & Atmospheric Sciences