New South Wales
Here's the proof it's A:
RRG - Insane wrote:
If an investigator has suffered Horror—whether faceup or facedown—
equal to or exceeding his sanity, that investigator becomes Insane.
• If an effect causes an investigator to suffer Horror in excess
of his sanity, he suffers all Horror from that effect before
becoming Insane and discarding his facedown Horror.