Which protozoan group exclusively consists of endoparasites that have an infectious spore-like stage in their life cycle
The Sporozoans are a diverse group of protists that includes various strictly parasitic organisms. According to the NCERT text, their most defining characteristic is the presence of a resilient, infectious spore-like stage within their complex life cycle. The most notorious and destructive example provided is Plasmodium (the malarial parasite), which continues to have a massive, staggering impact on the global human population.
Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.2 Kingdom Protista