Element in the noble ga family are considered stabled because their outer energy levels are

In octet state.

Explanation: For noble gases they are stable in state since their outer shell contain fully occupied having 8 electrons.

b) mutualism

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acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.