John's Parents Recorded His Height at Various Ages Up to 66

Multiple Choice

John's parents recorded his height at various ages up to 66 months. Following is a record of their results:
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$$\begin{array} { | l | l | l | l | l | l | } \hline \text { Age (months) } & 36 & 48 & 54 & 60 & 66 \\\hline \text { Height (inches) } & 35 & 38 & 41 & 43 & 45 \\\hline\end{array}$$ John's parents decide to use the least-squares regression line of John's height (y) on age (x) based on these data to predict his height at age 21 years. What can we conclude based on this information?

A) John's height (in inches) should be about half his age (in months) , on average.
B) John's parents will get a fairly accurate estimate of his height at age 21 years because the data are clearly correlated.
C) John's parents should not make such a prediction because it involves extrapolation.