Aligned Triple Exclusion

The cells A2, B4 and B6 can together accept various combinations of values. But some combinations of values can be excluded, because they would leave some cells with no potential values.

More precisely, the following combinations of values are not possible for the cells A2, B4 and B6:
0, 8 and 8 because the value can occur only once in the region
1, 8 and 5 because the cell B3 must contain 1 or 5
1, 8 and 9 because the cell B1 must contain 8 or 9
9, 8 and 5 because the cell B1 must contain 8 or 9
9, 8 and 9 because the cell B1 must contain 8 or 9

Because some potential values of B4 occur in none of the remaining combinations, they can safely be removed.