Answer:
The action most likely to decrease the number of discoveries scientists can make is "D. declining more private funding".
Funding is critical for research. It provides the resources for scientists to carry out their studies, purchase equipment, hire staff, and support various other operational costs. By declining more private funding, a research institution could be reducing its own ability to conduct a wide range of studies, potentially limiting the number of discoveries it can make.
While it's worth noting that options A, B, and C could also impact the scope and effectiveness of scientific research in various ways, lack of funding is most directly linked to a reduced ability to perform research and, by extension, make discoveries.