The two vectors (say A and B) of different magnitudes cannot be combined to give zero resultant since minimum value of combination is ІA-BІ which is not zero if AB.

The three vectors A, B and C of different magnitudes can be zero such that they form a closed triangle, then,

      A+B+C=0

or, C=-(A+B)

Hence, the sum of three vectors may be zero if vector sum of any two vectors is equal and opposite to the third vector.

Note: The vectors can give this result only if...

Makar disclosed that he had killed the merchant because he realized his mistake and Aksionov's suffering and now he wanted to make Aksionov release from the prison.

II)Cr2+ is reducing agent as its configuration changes from d4 to d3, when it is oxidized to Cr3+ .The d3 configuration have a half-filled t2g level which is very stable. On the other hand, the reduction of Mn3+ to Mn2+ results in the half-filled (d5) configuration which has extra stability hence Mn3+ acts as oxidizing agent.