Robert is studying a substance that is a made out of one element this means that

it means that Robert is studying a simple substance.

Explanation:

A simple substance can be a raw material, an atom, or an chemical element. It is an exhaustive investigation of only one element that is part of all the study subject. It’s important that when someone study only an element know that it can be a potencial part of a big factor, to be a gratest function inside the world.

the 4th option is the answer

hello

question:

when would a new household be started?

a.when the oldest male died

b.when a man and a woman married

c.when the house could not hold everyone

d.when a child was born

answer: us d when a child was born

hope this have a great day and brainlest