The answer is C (1 only).
• Statement 1 is correct: the biological receptors are chiral, so only one enantiomer has its groups in the correct three-dimensional arrangement to bind to the receptor, just as a right hand fits only a right-handed glove.
• Statement 2 is incorrect: enantiomers are stereoisomers, not structural isomers. Their atoms are bonded in the same way and they differ only in spatial arrangement. They have the same chemical properties, except in reactions with other chiral molecules.
• Statement 3 is incorrect: enantiomers have identical physical properties (melting point, boiling point, solubility), except that they rotate plane-polarised light to the same extent in opposite directions.
• A is wrong: statements 2 and 3 are false.
• B is wrong: statement 2 is false.
• D is wrong: statements 2 and 3 are false, and it leaves out statement 1, the correct reason.
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