What is the average value of the police feeling thermometer for individuals that are $18?($You should be able to complete this question after finishing Q$3,$ which asks you to create a dataframe with the average value of police feeling thermometer for every age in the dataset$).$

$68\mathrm{.}9$

$77\mathrm{.}9$

There are no $18-$year olds in the data frame

$20\mathrm{.}9$