Answer:
A) & B)
Explanation:
A) There are certain viruses that are present in both healthy and disease people.
Example: Polio virus is found in many human but it causes disesease in only 1% of human.
B) Viruses require host machinery for replication so they may not replicate in pure culture.
The postulate C is also violated, the virus may not produce disease in non-human experimental host because of inappropriate animal or vaccinated animal etc. Others exception includes, the same disease may be caused by various organisms and different organisms can also cause the same disease.
Answer: c
Explanation: because it helps by excreting
Each of the term is identified whether they arise from the ectoderm, mesoderm or the endoderm.
The thyroid arises from the endoderm.
The thymus arises from the ectoderm.
The anterior pituitary arises from the ectoderm.
