Answer:
A.
Explanation:
Miners were happy due to the result of the gold rush. they labored very hard for very little profit. Working in the Yukon Territory was not safe. To reach it, the ground had to be dug. Then the dirt had to be removed to get the gold.
In paragraph 2, what does the phrase "miners of all shapes and sizes" mean that many people were invited. This included food, clothing, transportation equipment, etc.
So, the short answer is: burning is irreversible because it involves a chemical reaction, while melting is reversible because it's just a phase change.
An electrolyte is a substance that releases ions when it is dissolved in water. Electrolytes are divided into salts, ions and bases. In this case, the electrolyte is H₃PO₄ as it releases H+ ions and PO₄⁻³ ions when it is dissolved in water.
Barium bromide is the chemical compound with the formula BaBr2. Like barium chloride, it dissolves well in water and is toxic.
The rate of reaction between oxygen and copper is higher at high temperature. The rate of reaction between oxygen and copper is lower at room temperature.
at high temperature copper penny will react with oxygen as shown below

The reaction does not occur easily at room temperature
We can say that the reaction between copper and oxygen is an endothermic reaction so the rate of reaction is high at high temperature.
The bond energy of oxygen molecules need energy to react with copper and form copper oxide.