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.
No.
The speed of sound in water depends on the temperature and pressure. As you go deeper, the pressure increases and the speed of sound increases.
This statement is false!
Around 90% of all the ozone contained in the atmosphere is accumulated in the stratosphere - this area is also called the ozone layer due to the high concentration of ozone.
Troposphere is below the stratosphere, and it's the one that's closest to the earth.
I think the second one since the largest bar (?) is for infants meaning that the population is mostly 4 year olds. Hopes this helps!
