Answer: The required probability is 
Step-by-step explanation:
Since we have given that
Number of spruce tree = 20
Number of maple tree = 50
Total trees = 70
We need to find the experimental probability that the next tree Colleen to get a spruce tree.
So, the probability would be :

Hence, the required probability is 
A is no observable trend, B is a positive linear trend, C is a negative linear trend, and D is an exponential trend