In which ways may Congress or a state legislature invalidate a statute?

The correct response indicates that Congress or a state legislature can invalidate a statute through both amendments and outright repeal. Repealing a statute means completely removing it from the books, effectively invalidating it. This is a definitive action that demonstrates the legislative body's authority to dispose of existing laws.

Amending a statute also serves as a means to invalidate specific provisions of the law if a legislature chooses to change its terms significantly. This process allows the legislature to reshape the statute's scope or intent, which, in practical terms, can render certain aspects of the original statute ineffective or obsolete. Through amendments, the legislature can express its updated policy perspective, effectively invalidating outdated legal standards or provisions.

The involvement of public opinion typically does not serve as a mechanism for invalidating statutes and is therefore not a direct method. Additionally, while judicial review plays a critical role in assessing the constitutionality of statutes, it is not a legislative action; it is a function of the courts. Thus, only the legislative actions of amending or repealing statutes are relevant here.