Ringworms is not caused by -

The correct answer is Option (3) → Trichoderma polysporum

In spite of its name, ringworm is caused by fungi, not by worms.

Option (1) Microsporum — A cause of ringworm. Microsporum is one of the three genera of fungi that NCERT names as causes of ringworm.

Option (2) Trichophyton — A cause of ringworm. Trichophyton is another of these fungi. It grows best in warm, moist skin folds.

Option (3) Trichoderma polysporum — Not a cause of ringworm. This is a useful fungus. It produces cyclosporin A, a drug that suppresses the immune system in organ-transplant patients. The name looks like Trichophyton, but it causes no disease.

Option (4) Epidermophyton — A cause of ringworm. Epidermophyton is the third ringworm fungus. As the name suggests, it attacks the outer layer of the skin.

NCERT Extract:
Common Diseases in Humans – “… Many fungi belonging to the genera Microsporum, Trichophyton and Epidermophyton are responsible for ringworms which is one of the most common infectious diseases in man. Appearance of dry, scaly lesions on various parts of the body such as skin, nails and scalp (Figure 7.3) are the main symptoms of the disease. These lesions are accompanied by intense itching.”
Chemicals, Enzymes and Other Bioactive Molecules – “… Another bioactive molecule, cyclosporin A, that is used as an immunosuppressive agent in organ-transplant patients, is produced by the fungus Trichoderma polysporum.”