She’s a replicant, isn’t she?

Deckard:
She’s a replicant, isn’t she?

Tyrell:
I’m impressed. How many questions does it usually take to spot them?

Deckard:
I don’t get it, Tyrell.

Tyrell:
How many questions?

Deckard:
Twenty, thirty, cross-referenced.

Tyrell:
It took more than a hundred for Rachael, didn’t it?

Deckard: [realizing Rachael believes she’s human]
She doesn’t know.

Tyrell:
She’s beginning to suspect, I think.

Deckard:
Suspect? How can it not know what it is?