Change the bond between the two carbon atoms in each molecule to a double or triple bond as needed to complete the structure. If the bond should remain a single bond, then you do not need to do anything to the bond. Do not change any other bonds in the molecules.

The first should be left asis because carbon already has 4 bonds/8 electrons

The second needs to have a double bond to give carbon 4 bonds/8 electrons

The third must have a triple bong between the carbons to give them both 4 bonds/8 electrons

Explanation:

Make sure Hydrogen only has 1 bond/2 electrons at all times. Carbon needs a total of 4 bonds/8 electrons