What was the main requirement for the development of life on Earth?
a. Exposure to sunlight
b. Absence of free oxygen
c. Simple sugars
d. Energization from electrical sparks
ANS: B
In laboratory experiments, gases and compounds thought to be similar to Earth's early atmosphere
were exposed to light, heat, and electrical sparks; the result was the production of simple sugars, small
proteins, and nucleotides. The absence of free oxygen seemed to be the key factor. Information can be
found in the section Life Probably Originated in the Ocean.
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Judge the following sentence according to the criteria given below: Oil spills in the ocean are not considered harmful BECAUSE crude oil in seawater at concentrations of 0.7 parts per billion kills or damages certain fish eggs
A) The assertion and the reason are both correct, and the reason is valid. B) The assertion and the reason are both correct, but the reason is invalid. C) The assertion is correct but the reason is incorrect. D) The assertion is incorrect but the reason is correct. E) Both the assertion and the reason are incorrect.
In an occluded front, the warm air sector is ________
A) on the ground B) above the ground C) north of the cold sector D) south of the cold sector E) in the center of the anticyclone
The gradient of a stream is
A. the volume of water passing a point per unit time. B. steepest near the stream's head (upper end). C. the product of velocity times width times depth. D. steepest near the stream's mouth (lower end).
Which stream order is the Ohio River, which feeds directly into the Mississippi River?
A. 0 B. 1 C. 2 D. 3 E. 4