Answer:
D. Because we cannot easily detect them.
Explanation:
Dark matter are called dark because using existing astronomical instruments we are blinded to them. Dark matter and dark energy are difficult to detect and properly observe. As we know that the whole universe is made up of matter, some of the matter do not interact with the electromagnetic radiations which makes undetectable.
A pie graph is the graph used to show how a part of something relates to the whole.
Answer: England and Canada
Explanation:
Yes
Answer: Out of the given options bonds connecting atoms in reactants break, and bonds connecting atoms in products form are the changes which takes place when a chemical change occurs.
Explanation:
A change that leads to the change in chemical composition of a substance is called a chemical change.
For example,
Here, bond between the reactant atoms nitrogen and hydrogen is broken down.
On the other hand, bond connecting the products that is and is formed.
Thus,, we can conclude that out of the given options bonds connecting atoms in reactants break, and bonds connecting atoms in products form are the changes which takes place when a chemical change occurs.