Why was Erik the Red able to explore Greenland in the 10th century AD?
A) He managed to sail the North Atlantic during a two-year period of minimal storms.
B) His explorations took place during a particularly warm climatic period.
C) There was no glacial ice in Greenland at the time.
D) Sea temperatures were cooler, so there was less propensity for storms.
B
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Secondary air pollutants are formed by
A) the evaporation of solvents and gasoline. B) the incomplete combustion of fuels. C) primary pollutants reacting with other compounds in the atmosphere. D) radioactive substances such as radon reacting with primary pollutants.
Air that rises from the tropics
A) will flow both north and south. B) continues into the stratosphere. C) generally subsides over the tropics. D) is controlled primarily by the Coriolis force. E) all of the above
What is the statistical recurrence interval for a flood of rank 2 in a data set that is 99 years long?
a. on average, once every 10 years b. on average, once every 20 years c. on average, once every 30 years d. on average, once every 40 years e. on average, once every 50 years
An important means of continental accretion is plutonism. Indicate whether the statement is true or false