The degree of static indeterminacy (Ds) for a 2D plane frame having 3 members, 3 rigid joints, and 2 fixed supports is:

Explanation

Ds = 3m + r – 3j = 3(3) + (3+3) – 3(3) = 9 + 6 – 9 = 6? Wait: Formula for rigid plane frame Ds = 3m + r – 3j. If m=3, r=6 (2 fixed supports = 3+3), j=4 joints -> 3(3)+6 – 3(4) = 3. Let us re-verify standard portal frame: 1-bay 1-story frame has m=3, j=4, r=6 => Ds = 3(3)+6 – 3(4) = 3. Let’s make options consistent.