The rare earth elements that are considered extremely important for widely used modern technologies include
a. scandium and yttrium
b. scandium, yttrium and the 15 lanthanides
c. yttrium, cobalt and the 15 lanthanides
d. scandium, nobelium and the 15 lanthanides
e. the 17 lanthanides alone
B
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A. Autotrophs B. Heterotrophs C. Chemoautotrophs D. Photosynthotrophs
The wavelength of radiation is ____ proportional to the energy carried per wave
A) directly B) not C) slightly D) inversely
What is the threshold mortality rate (the number of test organisms that die as a result of exposure to a potential pollutant) that determines if a pollutant is toxic or not?
The nature of volcanic eruptions is closely related to plate tectonics and magma type. Which of the following best describes basaltic magma?
A. relatively SiO2 rich and cool B. relatively SiO2 poor and cool C. relatively SiO2 poor and hot D. relatively SiO2 rich and hot