Protozoan and helminthic diseases are difficult to treat because Protozoan and helminthic diseases are difficult to treat because they replicate inside human cells. their cells are structurally and functionally similar to human cells. they do not reproduce. they have more genes than bacteria. they do not have ribosomes.

The correct answer is-their cells are structurally and functionally similar to human cells

Explanation:

Protozoan and helminths are eukaryotes so they have well define organelle inside their cell. Protozoans are animal-like protists which lives as parasite inside their host and helminths are parasite worms that takes their nutrient from their host cell.

As helminths and protozoans are eukaryotes and human are also eukaryotes, therefore, their cells are structurally and functionally similar to human cells.

As antibiotics are only made for bacteria because bacterial cell is different from human cell as bacteria are prokaryotes so antibiotic does not work of protozoan and helminths, as a result, they are difficult to treat because their cells resemble like animal cells.