In a B-tree, the concept of order is an important one. The order 'k' of a B-tree influences the number of keys in each of its non-root nodes.
The non-root nodes in a B-tree can have a number of keys ranging from ceil(k/2) - 1 to k - 1, where 'ceil' is the ceiling function that rounds up to the nearest whole number.
In the provided options, none of them satisfy this condition.
Option A says that the non-root nodes can have a maximum of (k-1)/2 keys. According to the formula we noted before, this is incorrect.
Option B indicates that the non-root nodes can have a minimum of (k-1)/2 keys, which is also wrong.
Option C suggests that the non-root nodes will have exactly (k-1)/2 keys. This is also incorrect as the number of keys can range from ceil(k/2) - 1 to k - 1.
Given these explanations, the most appropriate answer would be option D: None of the above, as this is the only option that fits with the explanation we formulated based on the number of keys that non-root nodes in a B-tree of order 'k' are reported to contain.
Answer: D. None of the above