Matching physical properties to compound structures Steps:

• Ethane (C2H6) is a nonpolar gas with very low mp (-183°C) and bp (-89°C), matching Y.
• Silicon(IV) oxide (SiO2) is a giant covalent solid with extremely high mp (1713°C), matching Z.
• Bromine (Br2) is a molecular liquid with low mp (≈-7°C) and bp (59°C), matching X (noting possible data approximation).
• Carboxylic acid (C_nH_{2n}O2) has hydrogen bonding, causing high bp (354°C) despite low mp (-63°C), matching W. Why D is correct:
• D assigns each compound to the data reflecting its bonding and state: SiO2 (giant covalent, Z), ethane (van der Waals gas, Y), Br2 (molecular liquid, X), carboxylic acid (H-bonded molecular, W). Why the others are wrong:
• A incorrectly assigns SiO2 to W (low mp unsuitable for giant structure).
• B incorrectly swaps SiO2 (to gas Y) and ethane (to solid Z).
• C identical to B, with same swap error.

Final answer: D