Find the incorrect statement.

• A

  Gene therapy is a genetic engineering technique used to treat diseases at molecular level by replacing defective genes with normal genes
• Correct answer
  B

  Calcitonin is a medically useful recombinant product in the treatment of infertility
• C

  Bt toxin is a biodegradable insecticide obtained from Bacillus thuringiensis
• D

  Trichoderma sp. is a biocontrol agent for fungal diseases of plants

Hence, the correct answer is option: 'B'.