How could you not know

BT: (comes into the stockroom) I've completely forgotten what I came in here for...
EM: bras, swimwear, nightwear, sports bras, nursing bras, clothing...
KM: zyklon b?
EM: what?
KM: the gas
EM: what?
KM: you know, the gas
EM: but what?
KM: the nazis...
EM: yeah, but what gas?
KM: (confused about EM apparently not knowing about the holocaust) the nazis gassed people...
EM: what gas...
KM: in aushwitgz!
EM: I know that! What has did you say! I didn't hear you!
KM: oh! zyklon b!
EM: that's what I was getting at! I wasn't saying 'what!?' like I didn't know it never happened!
KM: oh dear... I was getting worried!
EM: if anyone heard that I would have sounded like a right twat!