Structure and reactivity of 2-halo-1-butene Steps:

• Deduce structure: Straight-chain C4H8X (likely C4H7X, minor formula error) with X on C2 is CH3-CHX-CH=CH2.
• Confirm chirality: C2 bonds to H, X, CH3, and CH=CH2 (four distinct groups).
• Analyze elimination: Allylic halide undergoes HX loss mainly via E2, removing H from adjacent CH3 (C1), yielding CH2=CH-CH=CH2 (1,3-butadiene).
• Assess products: Single diene product, no additional structural or geometric isomers formed.

Why A is correct:

• A tetrahedral carbon with four different substituents (H, X, -CH3, -CH=CH2) defines a chiral center per stereochemistry rules.

Why the others are wrong:

• B: Elimination yields only one structurally isomeric product (1,3-butadiene), not two.
• C: The product (1,3-butadiene) lacks geometric isomerism; no cis-trans possible.

Final answer: A