(A) is definitely not sufficient

(B) in itself is also not sufficient

Lets look at A again

a/b = c/d

square both sides

a^2/b^2 = c^2/d^2

now sq rt

sqrt(a^2)/sqrt(b^2) = sqrt(c^2)/sqrt(d^2)

add 1 to both sides

we get

(root a^2 + root b^2)/root b^2 = (root c^2+ root d^2)/root d^2

using B this can be reduced to

|b| = |d|

similarly we can show that |a| = |c|

so both A and B together should be sufficient.

BTW this definitely is not a 2 min question

Sorry netigen, but I don't get how you reduced to b = d.

Could show it step by step please?

Thx

(root a^2 + root b^2)/root b^2 = (root c^2+ root d^2)/root d^2

We already know from (B)

(root a^2 + root b^2) = (root c^2+ root d^2)

Hence, the eq gets reduced to

1/root b^2 = 1/root d^2

root d^2 = root b^2

or |d| = |b|