(A) 1970s
(B) 1920s
(C) 1960s
(D) 1890s
🧠 Explanation:
- Scientists first identified coronaviruses in the 1960s while studying respiratory infections in both humans and animals.
- The name "corona" comes from the virus’s crown-like spikes observed under an electron microscope.
- Initially, these viruses were found in chickens (infectious bronchitis virus) and later in humans (causing common cold-like symptoms).
- So, the correct answer is the 1960s, when coronaviruses were first scientifically recognized in animals and humans.