Question

when a magician cut the lemon the blood comes out from the lemon. how is it possible?....

Answer 1

While cutting the lemon the magician uses a knife which was dipped into potassium permanganate.that's why it appears like blood or he can also add the potassium permanganate at the time of cutting.

Answer 2

When a magician cut the lemon the blood comes out from the lemon , the  magic / secret behind this is is the knife , yes it is knife , a flower named China Rose Flower(Hibiscus) has a different type of liquid which we get when we rub it on knife and when this liquids comes in contact with lime liquid it forms a red blood liquid ............. so this is the trick . 

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Best of luck ;)
ROYALJATT