The reactants are what is put into the reaction equation to get the product. In this case water and ammonia are put into the equation to get the product ammonium hydroxide.
The first choice is the correct answer:
Water and ammonia
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Answer:

Explanation:
Cesium Lewis dot structure would look like this:
·Cs, because it only has one valence electron. But, since it has a plus, that means we lost an electron. So, we have to get rid of the dot and you have:

Explanation:
It happens because particles of gas are in constant random motion. Thus they can collide with the walls of the container causing pressure on the walls.