There is no common set of synapomorphies (shared derived traits) that define a protist
a. Protists all share a common set of synapomorphies.
b. Protists are all more primitive than land plants and animals.
c. Protists do not share a single common ancestor.

Answer is option "b"

Explanation:

The "protista" word is composed from Greek word 'protisto' means " the very first". they are unicellular which contain a  nucleus and bound to the organelles.Researchers estimate that protists structure a connection between plants, creatures, and organisms as these three realms wandered from a typical protist-like progenitor, billions of years back. In spite of the fact that this "protists-like" precursor is a speculative creature, we can follow a few qualities found in present day creatures and plants to these old living beings.For example :- algae,plasmodium, amoeba etc.Hence, the right answer is option b "Protists are all more primitive than land plants and animals".