Physicist Joseph Weber performed ______ work in gravitational wave research in the 1960s and 1970s, conducting key
experiments that scientists later used as the basis for their own investigations that led to the ﬁrst veriﬁed detection of a
gravitational wave in 2015.
foundational
supplementary
repetitive
ineffective
Choice A is the best answer because it most logically completes the text’s discussion of physicist Joseph Webster’s
research on gravitational waves. In this context “foundational” means the basis on which something else develops. The text
indicates that Webster’s experiments in the 1960s and 1970s were earlier than, and “key” to, the work of later scientists in
the ﬁeld; thus, Webster’s work was foundational to the later scientists’ experiments and the eventual detection of a
gravitational wave in 2015.  
Choice B is incorrect because the text does not suggest that Webster’s work was supplementary, or an additional element of
an existing, larger project, but rather it was “the basis for” later experiments. Choice C is incorrect because the text does not
assert that Webster’s work was repetitive, or involved doing something the same way many times. Rather, the text indicates
that Webster’s work formed the basis for later investigations in the ﬁeld of gravitational wave research.  Choice D is incorrect
because the text does not state that Webster’s work was ineffective, or failed to produce the desired outcome. Rather, the
text strongly implies that Webster’s work was productive and extremely important to later work in the ﬁeld of gravitational
wave research.