I GIVE BRAIN LEST Which of the following is true about an estuary?

It is all fresh water.

It is all salty water.

It has very few organisms.

It is affected by tides.

Explanation:

An estuary is where a river pours into the ocean. So that means fresh water mixes with salt water here. This allows us to rule out choices A and B.

According to NOAA, their site says "Estuaries are one of the most productive ecosystems in the world, so there is a great diversity of animals and plants that live there". In other words, a lot of plants and animals live here, so we can rule out choice C.

Choice D is the answer because tides do affect estuaries. This is simply because the ocean is pretty much right next to it, or attached to it. So it's expected that a high tide would cause the water level in an estuary to increase.

b

step-by-step explanation:

b

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.