Write any three reason for the profuse use of plastic . although it is harmful .​

Plastics (i.e. synthetic polymers) are used frequently for many applications because they tend to be (a) easy to fabricate items with, by moulding, or other methods, (b) can be strong even though very lightweight, so useful for making items that require good physical strength, as well as things like packaging which need to be able to support the contents correctly, (c) relatively low cost (especially overall, when ease of fabrication is taken into account.

The "use" of plastics is not harmful per se, and plastics themselves are innocuous (one reason that they fail to readily biodegrade is that they do not interact with biological systems). But poor manangement of waste plastic can lead to problems.

Failing to recycle and reuse synthetic polymers can lead to those items not landfilled (which is a separate issue - ultimately we would run out of landfill sites) items ending up in the sea, rivers or in the general environment where they can be hazardous to wildlife, and look unsightly.

But that is down to poor management, and societal attitudes, not down to the fact that the items are made of plastics.

If we failed to manage sewage and simply discharged that into the streets or into rivers that would be a major problem too. But that doesn't mean we should "ban sewage" - just manage it in an effective way.

a rain shadow is a dry region of land on the side that is protected against the prevailing winds of a mountain range. the prevailing winds are the winds that occur most of the time in a particular place of the earth

prevailing winds carry air toward the mountain range. as the air rises up over a mountain range, the air cools, water vapor condenses, and clouds form. on this side of the mountains, called the windward side, precipitation falls in the form of  rain  or snow. this dry air produces a  rain shadow.

it's c. elements are placed in rows based on how may valencies electrons have.