Final answer:
The conjecture that Robyn will be 6 feet, 2 inches tall at the age of 22 is not valid because it assumes an ongoing growth rate that is biologically unlikely as growth typically slows down after puberty. Option d is correct.
Step-by-step explanation:
The given information states that Robyn has grown 2 inches every year for the past five years, and she is currently 15 years old and 5 feet, 4 inches tall.
The conclusion is that she will be 6 feet, 2 inches tall when she's 22 years old.
Let's check if the conclusion is valid based on the information provided:
Currently, she is 15 years old and 5 feet, 4 inches tall.
If she has been growing 2 inches every year for the past five years, her height at the beginning of this period (when she was 15 - 5 = 10 years old) was 5 feet, 4 inches - (5 years * 2 inches/year) = 5 feet, 4 inches - 10 inches = 4 feet, 6 inches.
Now, if she continues to grow 2 inches every year, when she turns 22, she will have grown an additional 7 years (22 - 15).
So, her height at 22 would be 4 feet,
6 inches + (7 years * 2 inches/year)
= 4 feet, 6 inches + 14 inches
= 5 feet, 8 inches.
The conclusion in the given conjecture is that she will be 6 feet, 2 inches tall when she's 22. Since 5 feet, 8 inches is less than 6 feet, 2 inches, the conclusion is not valid based on the provided information. Option d is correct.