Answer:
a) two/ darwinian and mass
Joseph Priestley is an 18th century natural philosopher who is famous in his experiments in electricity, air, optics and soda water. His works are qualitative rather than quantitative because he does not concern himself with theories but practical applications.
His experiment in electricity through replication of other experiments lead to the publication of his book known as History of Electricity. He observed that electricity conducts through certain materials like coal and that electricity flow from conductors to non-conductors.With this experiments he concluded that conductivity is related to chemical property.
Another experiment that lead to a famous discovery is placing a mice in closed container with mercuric oxide. He concluded that the mice survived sometime because of common air-oxygen. He then relate oxygen in respiration and its use in the blood.
It's the 4 the answer I hope it has served you
