Ionization confers polarity to phosphate heads

Steps:

• Recall that phospholipids have hydrophilic heads and hydrophobic tails.
• Identify the phosphate group in the head as key to hydrophilicity.
• Understand polarity arises from uneven charge distribution.
• Determine that water's solvent properties cause ionization, leading to polarity.

Why C is correct:

• Phosphates ionize in water by dissociating into charged species (e.g., PO₄³⁻), creating dipoles per the definition of polar molecules as those with partial charges.

Why the others are wrong:

• A: Hydrogen bonds form due to existing polarity, not cause it.
• B: Phosphate heads are soluble (hydrophilic) in water, opposite of insoluble.
• D: Covalent bonds do not form with water; interactions are non-covalent.

Final answer: C