Answer the following question given this paragraph: 

Viruses were assumed to exist before they were first seen with an electron microscope in the 1930s. Multiple hypotheses for viral origins have been proposed.


Q: Viruses were assumed to exist before they were first seen with an electron microscope in which decade?

 Choices:

- 1960's

- 1890's

- 1940's

- 1930 ' s

A:
1930 ' s
