Answer:
A standard system of measurement is very important because it helps us from making mistakes at the moment of doing calculations and correctly working...
One is correct, <span>carbon dioxide, methane, and water vapor are the three major greenhouse gases found in the atmosphere.</span>
<u>1) find molar mass of CH₄</u>

<u>2) determine moles of CH₄</u>

<u>3) multiply by avogadro's number</u>

I pick but I'm not sure about it though 1and3