Why are supernova explosions important for our existence?
A. They liberate from the star's core the heavy elements of which we and Earth are made.
B. They destroy wandering stars that might otherwise collide with our Sun.
C. They heat the interstellar medium and help keep Earth warm.
D. They sterilized the young Earth and allowed life to originate by killing off competing bacteria.
E. They bathe Earth in X-rays that may have helped life form.
Answer: A
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The temperature of the layer of gas that produces the visible light of the Sun is:
A) 3,500 K. B) 5,800 K. C) 12,300 K. D) 300,000 K. E) 15 million K.
Streak
What will be an ideal response?
A 120-V circuit has a breaker rated at 10 amps. If a 1050-W toaster is operating on this circuit, what is the largest number of 100-W bulbs that may also operate simultaneously on this circuit without tripping the breaker?
1.0 2.1 3.2 4.more than 2