A researcher is using a panel data set on n $=1000$ workers over T $=10$ years $($from $2001$ through $2010)$ that contains the workers' earnings, gender, education, and age. The researcher is interested in the effect of education on earnings. Determine whether each of the following is an example of unobserved person$-$specific or time$-$specific variables that are correlated with both education and earnings.

Unobserved motivation. $(1)\_\_\_\_\_\_\_\_\_$

Group of answer choices

person$-$specific

time$-$specific