Final answer:
Replacement of a natural fingernail typically takes between 4 to 6 months. The rate of growth can be influenced by various factors and can be used to estimate the time it would take to grow record-setting nails as listed in the Guinness Book of World Records.
Step-by-step explanation:
The question refers to the time it takes for a fingernail to be replaced naturally. The correct answer is c) 4 to 6 months, as fingernails typically take this amount of time to grow back completely under normal health conditions. Factors such as nutrition, health, and age can affect this rate of growth. For example, fingernails grow faster in younger people and during the summer.
Concerning the Guinness Book of World Records example, since adult nails grow at about 3 mm a month, you would divide the record lengths by the monthly growth rate to estimate how long it would take to grow such long nails. This is a straightforward application of division in mathematics related to real-life biological processes.