When did the Earth's crust form?
a. 2.9 billion years ago
b. 3.2 billion years ago
c. 4,600 million years ago
d. 4.6 thousand years ago
e. 12,000 years ago
C
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Evidence from geology suggests that initially the earth's atmosphere did not contain
a. O2. b. CO2. c. H2S. d. H2O. e. CH4.
The most obvious characteristic of annelids is the repeated segments that make up their bodies. They also have a complete digestive system, and a coelom. Which of the following is true of an annelid?
A. They have cephalization and an open circulatory system. B. Their gut is separated from their body wall. C. They have cephalization. D. Their gut is separated from their body wall and they have cephalization. E. They have an open circulatory system.
In a resting neuron, which ion is leaking out of the cell?
a. potassium only b. sodium only c. chloride only d. calcium only e. both sodium and potassium
In polygyny, one female mates with several males
____________________ Indicate whether the statement is true or false.