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.
Sunlight is the requirement of every single natural process on Earth.
Which of the following soil-building processes contributed most to making the shaded area on the map suitable for agriculture? Floods deposited rich silt over the land in a soil-building process that made the land fertile.
Answer: The answer is C.
Explanation: Soil includes 40-45 percent inorganic matter, 5% organic matter, 25% water, and 25% air. The right combination of air, water, minerals, and organic matter is essential for plant life to thrive. Microorganisms (both dead and alive) and decaying plants make up humus, the organic stuff in soil.
It's an air mass that develops over surface of a large body of water
