Final answer:
The correct answer is D. I, II and III only, as oncogenes, mutagens, and proto-oncogenes can cause the formation of a primary tumor, whereas metastasis is associated with the spread of an existing cancer.
Step-by-step explanation:
The formation of a primary tumour, or cancer, can be caused by various factors. First and foremost, oncogenes, which may be growth factors, protein kinases, GTPases or transcription factors, can cause cancer when they become constitutively active due to mutations. Similarly, mutagens are agents that cause mutations in DNA and can include substances like tobacco smoke, radiation, or chemicals. Lastly, proto-oncogenes are normal genes that can become oncogenes when mutated and contribute to cancer formation. However, metastasis refers to the spread of cancer cells to other parts of the body and does not cause the formation of a primary tumor, but rather secondary tumors.
Therefore, the correct answer to the question is D. I, II and III only, as metastasis is a result of cancer progression, not a cause of the initial tumor formation.