Explanation
Pairwise testing is a technique that tests all possible discrete combinations of each pair of input parameters. In this case, there are two main categories: Colour and Shape. Under Colour, there are three subcategories: Red, Blue, and Green. Under Shape, there are two subcategories: Triangle and Circle. There is an additional category under Triangle labeled Size of triangle, with two subcategories: Small and Large. To test all pairs of these parameters, we need to use a tool or an algorithm that can generate the optimal test cases. One such tool is Pairwise.org, which can produce the following test cases:
Table
Colour
Shape
Size of triangle
Red
Triangle
Small
Blue
Circle
-
Green
Triangle
Large
Red
Circle
-
Blue
Triangle
Small
Green
Circle
-
Red
Triangle
Large
Blue
Triangle
Large
These eight test cases cover all pairs of parameters, such as Red-Triangle, Red-Small, Blue-Circle, etc.
Therefore, the answer is B. 8. References = Pairwise Testing or All-Pairs Testing Tutorial with Tools and Examples, Pairwise Testing - What It Is, When & How to Perform?, All-pairs testing - Wikiwand, ISTQB Certified Tester Advanced Level Syllabus Technical Test Analyst (Section 3.2.3)