If a circle of radius R passes through the origin O and intersects the coordinates axes at A and B, then the locus of the foot of perpendicular from O on AB is :

If   ⁿC₄, ⁿC₅ and ⁿC₆ are in A.P., then n can be :

The total number of irrational terms in the binomial expansion of (7^1/5 – 3^1/10)⁶⁰ is :

The number of integral values of m for which the quadratic expression, (1 + 2m)x² – 2(1 + 3m)x + 4(1 + m), x $$ \in $$ R, is always positive, is :