Geometric Isomerism in Alkenes Steps:

• Identify the double bond carbons and their substituents in each option.
• Check if each carbon of the double bond has two different substituents (required for cis-trans isomerism).
• Eliminate options where at least one carbon has two identical substituents.
• Select the option meeting the condition.

Why A is correct:

• In CH₃CH=CHCH₃ (2-butene), the double bond carbons each have H and CH₃ as different substituents, allowing cis and trans forms.

Why the others are wrong:

• B: CH₃CH₂CH=CH₂ (1-butene) has one carbon with two H atoms, preventing isomerism.
• C: CH₃CH=CH₂ (propene) has one carbon with two H atoms.
• D: (CH₃)₂C=CH₂ has one carbon with two CH₃ groups.

Final answer: A