Answer:
A. What length of time is best to use for the firing of pottery to make it strong?
Explanation:
Point A
What length of time is best to use for the firing of pottery to make it strong?
This is a scientific question for Nancy since while making pots from black mud, it is very important to know how much time is required to fire the pot in order to make it strong. Because if we fire it for too long the pot may be become too hot and will eventually crack. While if we fire for less time it will not become hard enough to withstand its shape. So knowing the proper time to fire the pot is very essential in pottery.
Point B, Point C and Point D are not scientific investigations since it includes ones likes and dislikes, quantities and numbers of goal scored which is not scientific.
Hence, option A is the correct answer.