Alkene structure, isomerism, and HBr addition rules

Steps:

• Draw 2-methylbut-1-ene: CH2=C(CH3)CH2CH3, with terminal double bond.
• Check geometrical isomers: C1 has two H atoms (identical substituents), so no cis-trans isomerism possible.
• Predict HBr addition: Markovnikov rule directs H to C1 (more hydrogens) and Br to C2, yielding CH3CBr(CH3)CH2CH3 (2-bromo-2-methylbutane).
• Compare to Student 2's product: 1-bromo-2-methylbutane is BrCH2CH(CH3)CH2CH3 (anti-Markovnikov, not major).

Why D is correct:

• Both statements fail: no geometrical isomers due to identical substituents on C1 (definition of cis-trans isomerism), and major HBr product is 2-bromo-2-methylbutane per Markovnikov's rule (H adds to carbon with more H's).

Why the others are wrong:

• A: Both students incorrect, as explained.
• B: Student 1 wrong; no geometrical isomers.
• C: Student 2 wrong; product is not 1-bromo-2-methylbutane.

Final answer: D