All of the following are helminths except:

• A. Schistosoma mansoni
• B. Taenia solium
• C. Escherichia coli
• D. Ascaris lumbricoides

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the term 'helminths'. Helminths are parasitic worms, which include flatworms (like flukes and tapeworms) and roundworms (nematodes). They are multicellular organisms that infect hosts and cause various diseases.
2. Step 2: Identify each organism listed in the problem. Schistosoma mansoni is a type of blood fluke (a flatworm), Taenia solium is a tapeworm (a flatworm), and Ascaris lumbricoides is a roundworm (a nematode). All three are helminths.
3. Step 3: Recognize the exception. Escherichia coli is a bacterium, a single-celled prokaryotic microorganism, not a worm or helminth.
4. Step 4: Conclude that since Escherichia coli is a bacterium and not a worm, it is the correct answer to the question asking for the organism that is NOT a helminth.
5. Step 5: Summarize that the key to solving this problem is knowing the classification of each organism and understanding that helminths are multicellular parasitic worms, whereas bacteria like Escherichia coli are not.