Answer:
Since this is old, im just gonna get these points, don't wan't them to go to waste lm.ao
Explanation:
<span>If thermal energy (heat) must be added to a chemical reaction in order for the reaction to take place, the reaction is endothermic. </span>
An ionic compound consists of a metal AND a non-metal.
<em>Option A:</em>
Oxygen and fluorine are non-metals.
<em>Option B:</em>
Sodium and aluminium are non-metals.
<em>Option C:</em>
Calcium is a metal and chlorine is a non-metal.
<em>Option D:</em>
Nitrogen and sulfur are non-metals.
Thus, the answer is C.
Methane was unusually high is the correct option. Hence, option B is correct.
<h3>What is methane?</h3>
Methane is the simplest member of the paraffin series of hydrocarbons and is among the most potent greenhouse gases. Its chemical formula is .
As the ice compacts over some time, tiny bubbles of the atmosphere or surroundings including greenhouse gases like carbon dioxide and methane—press inside the ice. These air pocket “fossils” give samples of what the atmosphere was kind when that layer of ice formed.
Based upon past studies and insights from current GHG levels, we assume that atmospheric levels of carbon dioxide and methane were unusually low.
Learn more about methane here:
brainly.com/question/2127750
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