The five cells B1, B7, B8, B9 and A2 form a VWXYZ-Wing.
The four cells B1, B7, B8 and B9 are an Almost Locked Set (ALS) that is linked to the bivalue cell A2 through the value 7, so if the value 8 was eliminated from all five Wing cells then the remaining value 8 of A2 leaves just three values to fill the four ALS cells, which is invalid; so 7 is "locked into" these five Wing cells, hence 8 can be removed from cells which see all 8's in the Wing.
Therefore we can remove A7-8.