The average speed would be 600 km/hr.
Step-by-step explanation:
Let the original speed be 'x'
Let the decreased speed be 'x-200'
Distance = 600 km
Time increased by 30 minutes
According to question, it becomes,

So, The average speed would be 600 km/hr.
By graphing the polynomial, we conclude that there is only one real root, so the correct option is A.
<h3>
How many roots has the given polynomial?</h3>
We have the polynomial:

To see how many real roots this polynomial has, we can graph it and see how many times the graph intercepts the x-axis.
The graph can be seen below:
There we can see that there is only one intercept, so there is only one real root.
So the correct option is A.
If you want to learn more about polynomials:
brainly.com/question/4142886
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