<h2>
contains both covalent and ionic bonds.</h2>
Explanation:
A covalent bond is formed when an element shares its valence electron with another element. This bond is formed between two non metals.
An ionic bond is formed when an element completely transfers its valence electron to another element. The element which donates the electron is known as electropositive element or the metal and the element which accepts the electrons is known as electronegative element or non metal.
a. 
contain covalent bonds as they are made up of non metals only.
b. 
contain ionic bonds as they are made up of sodium metal and fluorine non metal.
c. 
contain covalent bonds as they are made up of non metals only.
d. contain ionic bonds between 
and 
and covalent between N and H in 
Learn more about ionic and covalent bonds
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Answer:
1) Big Bang Theory
2) we are in a phase of the big bang theory
Explanation:
So for number 1 the answer is the -big bang theory- and number 2 there is a theory that pretty much says that were in a constant cycle. what I mean is theoretically in a couple million years the entire universe will form together again into another dense ball and repeat the process. So basically the universe is still in the "expanding phase" and that's what backs up the theory of the big bang (the fact that were in one of the big bang theory's "phases")
A common use of bases is to reduce indigestion. Hence, option D is correct.
<h3>What is the base?</h3>
A base is a substance that can neutralize the acid by reacting with hydrogen ions.
Bases are substances whose solutions have a pH value of more than 7. Bases are bitter in taste.
Whereas acids are the substances whose solutions have a pH value of less than 7. Acids are sour in taste.
When an excess of acid is formed in the human stomach then an antacid tablet which is basically a base is consumed that helps in reducing indigestion.
Therefore, we can conclude that the common use of bases is to reduce indigestion.
Learn more about the base here:
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Answer:
The higher up an object is the greater its gravitational potential energy. ... As most of this GPE gets changed into kinetic energy, the higher up the object starts from the faster it will be falling when it hits the ground. So a change in gravitational potential energy depends on the height an object moves through.
