Question

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 bacterias 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 flemings determination to find a cure for bacterial infections and florey and chains assiduous labor that were responsible for the development of these life - saving drugs.
what is the meaning of assiduous as used in the passage?
diligent
fast - moving
unrecognized
unexpected

Explanation:

The passage mentions that scientists Howard Florey and Ernst Boris Chain did "careful and thorough research" to develop antibiotics using penicillin. The word "assiduous" should have a meaning similar to words that describe such dedicated work. "Diligent" means showing care and effort in one's work, which fits the context. "Fast - moving" is about speed, which is not relevant here. "Unrecognized" and "unexpected" do not relate to the nature of their research work described.

Answer:

dilig