If a commodity is provided free to the public by the Government, then

the opportunity cost is zero.
the opportunity cost is ignored.
the opportunity cost is transferred from the consumers of the product to the tax-paying public.
the opportunity cost is transferred from the consumers of the product to the Government.

Answer

the opportunity cost is transferred from the consumers of the product to the tax-paying public.

(a) Opportunity cost is not zero just because the good is free to the user; resources used still have alternative uses. Verdict: Incorrect.
(b) Opportunity cost is not ignored in economic terms; it is still borne by someone even if users do not pay directly. Verdict: Incorrect.
(c) When government provides a commodity free, the cost is financed through public revenue, mainly taxes; thus the burden shifts from direct consumers to the tax-paying public. Verdict: Correct.
(d) The Government itself does not ultimately bear the cost independently; it raises resources from taxpayers/borrowers, so saying it is transferred simply to the Government is incomplete. Verdict: Incorrect.