Bivalue Universal Grave type 1

If the value {0} were removed from the cell {1}, the Sudoku would exhibit a Bivalue Universal Grave pattern (or BUG).

In a BUG, each value that remains in a row, column or block has exactly two possible positions in that row, column or block; and each empty cell has exactly two possible values. A Sudoku having a BUG has zero, two or more valid solutions.

Because a valid Sudoku has exactly one solution, the BUG cannot be part of it. The only way to avoid the BUG is if the cell {1} contains the value {2}. The values {3} can therefore be removed.