Step 1: Know the rule for cis trans.
Geometrical isomerism, also called cis trans, needs a carbon to carbon double bond. Also each double bond carbon must carry two different groups.
Step 2: Check 2-butene.
2-butene is $\text{CH}_3\text{-CH=CH-CH}_3$. Each double bond carbon has one $\text{CH}_3$ and one H, which are different. So it can show cis and trans forms.
Step 3: Check 1-butene.
1-butene is $\text{CH}_2\text{=CH-CH}_2\text{-CH}_3$. One double bond carbon has two H atoms, which are the same. So it cannot show this isomerism.
Step 4: Check propene.
Propene is $\text{CH}_3\text{-CH=CH}_2$. The end carbon again has two H atoms, which are the same. So no cis trans forms are possible.
Step 5: Check 2-methylpropene.
Here one double bond carbon has two H atoms. Since they are the same, there is no geometrical isomerism.
Step 6: Final choice.
Only 2-butene has two different groups on each double bond carbon, so it shows geometrical isomerism.\[ \boxed{\text{2-Butene}} \]