About 75% of the mass of the visible universe is composed of which element?
a. Helium
b. Iron
c. Hydrogen
d. Silicon
c
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Galileo used a telescope to observe the phases of the Sun
a. True b. False Indicate whether the statement is true or false
The image formed in a plane mirror is
A) at the same distance in front of the mirror as the object is in front of the mirror. B) at the same distance behind the mirror as the object is in front of the mirror. C) at a shorter distance behind the mirror than the distance the object is in front of the mirror. D) a real image behind the mirror. E) at a larger distance behind the mirror than the distance the object is in front of the mirror.
Pangaea is believed to have broken up about how many years ago?
a. 2000 million b. 2 million c. 20 million d. 200 million
A substance that speeds up a chemical reaction but is not consumed is a(n) ______________
Fill in the blank(s) with correct word