Speed = (distance covered) / (time to cover the distance)
= ( 8.45 km) / (0.65 hr)
= (8.45 / 0.65) km/hr
= 13 km/hr
"Changing water salinity" is the most significant challenge for organisms that live in estuaries.
<u>Answer:</u> Option D
<u>Explanation:</u>
For estuaries, alkalinity levels are usually the maximum at a river's mouth where the ocean water falls for, and the minimum upstream where freshwater falls in. Although salinity vary throughout the tidal cycle. In estuaries, salinity rates usually decrease in spring as snow melt and rain raises the freshwater flow from streams and groundwater.
It influences the chemical environments within the estuary, especially the dissolved oxygen (DO) levels in the water. The level of oxygen that would get dissolved in water or its solubility get declined when the alkalinity rises.
<span>d. The parallaxes beyond a few thousand light years are
too small to be measured with common instruments.
I'm not sure that parallax can even be used out to a few
thousand light years.
The NEAREST star to Earth has the BIGGEST parallax.
The star is Alpha Centauri. It's only 4 light years away
from us, and its parallax is 0.000206 of a degree !
I have no idea how astronomers can measure angles
so small ... and that's the BIGGEST parallax angle of
ANY star.</span>
