In alkenes, there are four groups bonded to the carbons that constitute the carbon-carbon double bond. Which of the following situations produces cis-trans isomerism?

A) when all four groups are the same
B) when one double-bonded carbon is bonded to two identical groups and the other double-bonded carbon is bonded to two other identical groups
C) when three of the four groups are the same, but the fourth group is different
D) none of these