Question

The cross product of two vectors A and B is zero if

• A. A is a null vector and B a proper vector
• B. A is a proper vector and B is a null vector
  
• C. A and B are both null vectors
• D. A and B are proper vectors parallel to each other

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A A is a null vector and B a proper vector
B A is a proper vector and B is a null vector

C A and B are both null vectors
D A and B are proper vectors parallel to each other

$\overrightarrow{A}\times \overrightarrow{B}=AB\sin \theta =0$ if $A=0$ or $B=0$ or $\theta =0^{\circ }$.
Hence all the four choices are correct.