There are<span> seven </span>continents<span>: North America, South </span><span>America, Asia, Europe, Africa, Antarctica and Australia.</span>
<u>Answer:</u>
a) The land which supplies water to a "river system" is called a <u>watershed.
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b) Pollution from a single, identifiable source is called <u>point source pollution</u>.
c) Pollution which is very difficult to link to a particular origin is called <u>non-point source pollution.
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<u>Explanation:</u>
- A watershed serves as a feeder to the rivers in a particular river system.
- When a certain type of pollution has a single point of origin, it is called 'point' source pollution.
- When a certain type of pollution "cannot be traced back" to a single origin and is recognized to have multiple sources, it is known as 'non-point' source pollution.
