a)When silver nitrate comes in contact with skin, it is reduced to white color metallic silver.In most cases, a black stain appears due to formation of finely divided silver which has black color.

The black color is due to the decomposition of the Ag+ ion into Ag, silver. Silver nitrate will slowly decompose with the silver ion reverting to elemental silver. The microscopic particles of silver are so small that they absorb light instead of reflecting it, and so appear black, instead of silver....

Yes, a vector which has zero magnitude is also a vector in case of two vectors travelling in opposite directions with equal magnitudes. At this case, the resultant vector has zero magnitude but it is still a vector. We call it a null vector.

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.

Aksionov is the protagonist of the story "god sees the truth but waits" written by Leo Tolstoy. He is a young merchant. He is a handsome, fair-haired, curly-headed fellow, full of fun and very fond of singing. He used to drink much before marriage but later on, he changed himself and became a good man. He had virtuous qualities such as faith, forgiveness, freedom, and acceptance. His comfortable life is disrupted when he is framed for a murder he didn't commit and was sent to a...