The correct option is D c>max(a,b)
Given, Circle equation as , x2+y2=c2 and
Ellipse equation as ,x2a2+y2b2=1
Both equation has center as (0,0)
Vertices of circle equation are (c,0),(−c,0),(0,c),(0,−c)
Vertices of ellipse equation are (a,0),(−a,0),(0,b),(0,−b)
for ellipse to contain within circle, c>a,c>b
∴C should be greater than max(a,b).