We need optics to help aid people who have short or long sightedness.
we need optics to be able to watch TV
we need optics to be able to use the internet at high speeds
there are a tonne of reasons why we need optics.
<span>25,000 miles per hour
hope that this helps</span>
Answer:

Explanation:
the variations in riser height or tread depth should not be grater than
that is equal to 9.5 mm but the maximum riser height should be the
but variation in riser height should not exceed to
. The minimum riser height should be 7 inches which is equal to the 178 mm