I believe the answer is 2: multiple ecosystems in a biome
Answer:
The sun, earth, and moon are held together by gravity, and they interact in lots of ways. The moon orbits the earth because of the pull of the earth. And the earth orbits the sun because of the pull of the sun. Because of the way they move relative to each other, we see phases and eclipses
The three substances that cause a double displacement reaction to occur are:
(i) Ionized compounds. These are usually water.
(ii) A gas that bubbles out a solution.
(iii) A precipitate.
In double displacement reaction is where two new compounds are formed when two parts of two compounds switch places. For example; when sodium chloride combines with silver nitrate, the two new compounds formed are Sodium nitrate and silver chloride reason being sodium and silver switched places.