Animals that have only a single body opening that serves as both mouth and anus include
A) cnidarians only.
B) cnidarians and flatworms.
C) cnidarians, flatworms, and roundworms.
D) cnidarians and sponges.
B
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Cratons are generally of low elevation and old in age
Indicate whether the statement is true or false
Environmental refugees are people who have to leave their homes and sometimes their countries because of ____.
A. social injustices B. political problems C. religious persecution D. war E. environmental degradation
Abrasion is distinguished from plucking in that
A) abrasion is a smooth scraping, while plucking is a more jagged gouging of the bedrock. B) abrasion is a jagged gouging, while plucking is a smooth scraping of the bedrock. C) abrasion is an erosional feature, while plucking is a depositional feature. D) abrasion is a depositional feature, while plucking is an erosional feature.
Although George Airy's hypothesis better explains surveying errors in the Himalayas, John Pratt's hypothesis better explains
A) how the Himalayas formed in the first place. B) elevation differences between oceans and continents. C) surveying errors in the Appalachian Mountains. D) isostatic adjustments to ice-age glaciers.