In an electron dot diagram of ethylene (c2h4), how many double bonds are present? a. none b. one c. two d. three

Ethylene, also known as ethene, has two carbon atoms and four hydrogen atoms.

The carbon atoms in ethene exhibit a valency of 4; therefore, in order to complete their outermost shell, the carbon atoms form a double bond with one another. 
Thus, the number of double bonds present in a molecule of ethylene is 1.

The answer is a) carbon-12