Which of the following elements is the most reactive - potassium - lithium - sodium - rubidium

Elephants in the savanna regions of africa dig holes in dried up river beds to reach water lying just below the surface. these holes provide drinking water for other animals as well. so, without the elephants, many animals might otherwise die from lack of water during the dry season. the location in which the elephants live is an example of a/n and the role they play in creating water holes is an example of a a) ecosystem; habitat b) community; niche c) habitat; niche d) niche; habitat

Idon’t know the answer and i’ve been stuck on it for a while now skskskskks

What happens during the experiment stage of the scientific method