PaymentProvider.charge(amount) is documented to accept any amount greater than 0. LegacyBankProvider extends PaymentProvider throws if the amount is below 100. Which statement is correct?

The right answer is "It violates LSP because it strengthens the precondition". A subtype may accept more inputs than its base, never fewer. The base contract allows any amount above 0. The subclass rejects amounts below 100, so it demands more from its inputs. This is called strengthening the precondition. It breaks callers that rely on the base contract.

The option "It is fine under LSP, because subclasses may add stricter validation" is wrong. Matching signatures is not enough, because LSP is about behaviour, not just method shapes.