Answer:
b. flat rotation curves in spiral galaxies
Explanation:
Dark matter accounts for majority of the matter in the universe (about 85%). It is considered to be composed of subatomic particles which are yet to be discovered. Dark matter cannot be observed because it does not emit light that can be detected. Only its gravitational effect is visible.
Astronomers when calculated the mass of the visible matter and tried to account for the observed speed of stars in the galaxy, there was a mismatch. To understand what caused this mismatch, astronomers gave name to the invisible matter as the Dark Matter.
The expected velocity of stars should decrease away from the near the center of the galaxy but a constant velocity of stars was observed that is a relatively flat rotation curve was obtained.
Thus, flat rotation curves in spiral galaxies in an evidence of Dark Matter.
The Great Lakes were formed during the last ice age.
<span>limestone is a hard sedimentary rock, made mostly of calcium carbonate or
dolomite, and it's used as building material & in the making of cement.</span>
Explanation:
1. Ethanol is a renewable fuel and is used in agricultural feed like , sugarcane , potato , corn , etc .
Hence , it is important to use ethanol as a fuel .
2.
Yes , it is necessary for each and every individual to use ethanol fuel for their day to day activities .
3.
Yes ,
the production of ethanol can be subsidized , by giving the tax rebate to the workers of the bio ethanol .
For example , in 2005 and 2009 , 17 billion USA dollars ethanol were subsidized .
Answer:
Unfavourable climate
Explanation:
Africa mainly in the Northern parts face a problem of unfavourable climate is too much sunshine that leads to drought and starvation