"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.
Answer:
a)
b) 
Explanation:
The net force on the car must produce the centripetal acceleration necessary to make this circle, which is 
. At the top of the circle, the normal force and the weight point downwards (like the centripetal force should), while at the bottom the normal force points upwards (like the centripetal force should) and the weight downwards, so we have (taking the upwards direction as positive):
Which means:
The limit for falling off would be 
, so the minimum speed would be:
Answer: k = 1163.72 N/m²
Explanation: if the bow obeys hook's law, then force is proportional to extension.
F = ke.
F= Force = 263 N
k = force constant
e = extension = 0.226m
263 = k * 0.226
k = 263/ 0.226
k = 1163.72 N/m²
A force can cause a resting object to move, or it can accelerate a moving object by changing the objects speed or direction
