Read the passage and then answer the question. While most scientific findings are the result of deliberate and carefully designed experiments, occasionally a major discovery happens in a more fortuitous way. One such example is the discovery of penicillin in 1928 by the Scottish bacteriologist Alexander Fleming. After working as a field doctor during World War I and witnessing how many soldiers died needlessly from bacterial infections, Fleming recognized the exigency of finding a chemical that could fight these afflictions . He began to conduct experiments by growing bacteria in Petri dishes and treating them with various chemicals . Unfortunately, none of the chemicals he tested proved effective at stopping the bacteria's growth. One day, as he was cleaning his laboratory,Fleming noticed that some mold had contaminated one of his Petri dishes. Upon closer inspection, he realized that the mold had actually destroyed the bacteria surrounding it. Fleming took a sample of the mold and discovered that it was from a genus of fungus known as Penicillium. He named the bacteria-killing substance emitted by this fungus penicillin and published his findings in a scientific journal. Through careful and thorough research, scientists Howard Florey and Ernst Boris Chain were later able to use penicillin to develop the first antibiotics-drugs that are used to this day to fight serious infections like pneumonia. Thus although the initial discovery of penicillin occurred by accident it was ultimately Fleming's determination to find a cure for bacterial infections and Florey and Chain's assiduous labor that were responsible for the development of these life-saving drugs. What is the meaning of assiduous as used in the passage? fast-moving diligent unrecognized unexpected