Let's analyze the matrix:

3	8	10	2	?	1
6	56	90	2	20	0

The first row is: 3, 8, 10, 2, ?, 1
The second row is: 6, 56, 90, 2, 20, 0

We need to find the relationship between the two rows to determine the value of '?'.

Upon closer inspection, let's explore a potential relationship:

1. $3 \times 2 = 6$
2. $8 \times 7 = 56$
3. $10 \times 9 = 90$
4. $2 \times 1 = 2$
5. $? \times 4 = 20$

From the 5th point, we can solve for '?': $? \times 4 = 20$
$? = 20 / 4 = 5$

Thus, the missing number at '?' is 5.

The correct answer is A. 5.