Trilobites lived during which era?
a. Paleozoic
b. Cenozoic
c. Mesozoic
d. Archeozoic
a
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In the context of a big bang model, identify a true statement about the flatness problem
A) It is the peculiar circumstance that the early Universe's average density was much more than the critical density but it was still flat. B) It is the peculiar circumstance that the actual density of the Universe will always be equal to the critical density and will always remain flat. C) It is the peculiar circumstance that the early Universe must have contained exactly the right amount of matter to make space-time flat. D) It is the peculiar circumstance that the early Universe's average density was considerably less than the critical density but it was still flat.
Photography Optics: A slide projector needs to focus the image of a 24.0-mm × 36.0-mm slide onto a square screen 1.50 m on each side. You want to fill the screen as completely as possible without any of the image falling beyond the screen. Due to space constraints in the projector, the slide must be placed 10.5 cm from the lens.(a) What magnification does the projector produce?(b) How far from the lens should the screen be placed?(c) What focal length projector lens is needed?
What will be an ideal response?
What do astronomers consider heavy elements?
A) elements that are heavier than iron B) elements that are heavier than carbon C) elements that are heavier than hydrogen D) elements that are heavier than uranium E) all elements besides hydrogen and helium
The "oxygen crisis" occurred around
A) 2 billion years ago B) 3.5 billion years ago C) 2.5 billion years ago D) 4 billion years ago