Which of the following tools was responsible for advancing our knowledge of cells over the past 400 years?

Has to be a microscope Ong

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey