The answer is c. number of protons and d. atomic number. The proton number can identify an element. And also the atomic number is equal to the number of protons.
Answer: COMBINED FORCES
When forces act in the same direction, they combine to make a bigger force. When they act in opposite directions, they can cancel one another out. If the forces acting on an object balance, the object does not move, but may change shape.
Explanation:
To completely convert 9. 0 moles of hydrogen gas (h2) to ammonia gas, 3.0 moles of nitrogen gas (n2) are required.
<h3>What are moles?</h3>
The mole is a SI unit of measurement that is used to calculate the quantity of any substance.
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The given reaction is 
By the stoichiometry rule of ratio hydrogen: nitrogen
3 : 1
The reacted moles of nitrogen is equals to H/3 moles of reacted hydrogen
So, moles of nitrogen

Thus, 3.0 moles of nitrogen gas (n2) are required.
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Light bulb -it produces heat and light
toaster - it produces heat and the metal strips glow producing light
B. Hydra, because Hydra<span>are an ideal class of </span>Cnidaria<span> to research and on which to run tests.</span>