A fisher man targets at the tail of fish in pond to kill it .why give reason?

Do you mean aim a spear at the fish while the fisherman is standing on the shore? It may be because of the refraction index of water. You know how when you reach into water to grab something you miss? Or if you stick a straw in a glass of water it appears to bend? You have to account for that and learn to aim not quite at your target as you would if you were both on land or both underwater.

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6

c. magnitude and direction