Scientists believe that the first life forms to appear on planet earth were probably similar to which modern organisms?
a) viruses
b) bacteria
c) plant cells
d) animal cells

The correct answer is -

B) bacteria.

Explanation:

The first life form on Earth is considered to be a microbe with single-cell, lacking a nucleus and membrane bound subcellular compartments, known as prokaryotes (bacteria).

They seemed to have first appeared around four billion years back, just a few hundred million years after which Earth formed itself.

Thus, scientists believed that the first life forms to appear on planet Earth were similar to bacteria.