Answer:
[tex]\boxed{\text{D. 11.6 lb}}[/tex]
Step-by-step explanation:
The mean is the sum of the weights divided by the number of weighings.
[tex]\text{Mean}= \dfrac{13.5 + 12.5 + 10.5 + 11.2 + 11.2 + 10.8 + 9.5 + 13.4 + 11.5 + 11.8}{10}\\\\= \dfrac{115.9}{10} \approx \mathbf{11.6}\\\\\text{Heather is predicting that Sally will weigh } \boxed{\textbf{11.6 lb}}[/tex]