If AAA and BBB are 3×33 \times 33×3 matrices and AB=0AB = 0AB=0, which of the following is necessarily true?
A=0A = 0A=0 or B=0B = 0B=0
rank(A)+rank(B)≤3rank(A) + rank(B) \leq 3rank(A)+rank(B)≤3
rank(A)=rank(B)rank(A) = rank(B)rank(A)=rank(B)
det(A)=0det(A) = 0det(A)=0 or det(B)=0det(B) = 0det(B)=0