Question:
The number of teeth and the age of a person vary
(a) directly with each other
(b) inversely with each other
(c) neither directly nor inversely with each other
(d) sometimes directly,and sometimes inversely with each other
Solution:
(d) The number of teeth and the age of a person vary sometimes directly and sometimes inversely with each other, we cannot predict about the
number of teeth with exactly the age of a person. It change with person-to-person.
Hence, option (d) is correct.