Answer:
Option C
Explanation:
Let the radius circle with least area be r
Then, then coordinates of centre= (0,4,-r)

Since, circle touches the line y=x in first quadrant
∴
∣0−(4−r)√2∣=r
⇒ r−4=±r√2
⇒ r=4√2+1 or 41−√2
But r≠41−√2 [∵41−√2<0]
∴ r=4√2+1=4(√2−1)