Question

$21 \times \frac{?}{?} \times \frac{?}{?}$
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Answer 1

Step-by-step explanation:

Pollution is the introduction of contaminants into the natural environment that cause adverse change.

There are 4 types of pollution:-

1. Water Pollution

2. Air Pollution

3. Land Pollution

4. Noise Pollution

Answer 2

Answer:

Compare the speeds of light of wavelength 4000Å (violet light) and 8000Å (red light) in vacuum.