Vectors can be defined as
(a) animals carrying the infecting agents from sick person to another healthy person
(b) microorganisms which cause many diseases
(c) infected person
(d) diseased plants
Answer: The correct answer is (a) animals carrying the infecting agents from a sick person to another healthy person
Solution: The animals which carry infectious agents such as viruses, bacteria, protozoans etc. from an infected person to a healthy host are also termed intermediaries or vectors. The most common example for Vectors is mosquitoes which cause many diseases such as Malaria, Dengue fever etc.
Hence, the correct answer is A.