​Which of the following is a weak electrolyte?

(A) Sodium chloride (NaCl)

(B) Sodium hydroxide (NaOH)

(C) Water (H₂O)

(D) Copper sulphate (CuSO₄)

Hi,

Water is a weak electrolyte because at room temperature small fraction of OH^- and H⁺ is formed by the dissociation of water molecule. 

Water is a weak electrolyte.

H₂O  $\iff$ OH^- +  H⁺

Regards