The answer is "YEAR"
I know that congress must meet once a year. It highlighted where the previous answer was on every subsequent question. Not necessarily the answer of the previous question, the place (a,b,c or d) where the last answer was (if that makes sense). Only if it brought some of the answers with the next question was the previous answer highlighted. The highlighted answer wasn't my answer on question #4 as I hadn't answered the question yet. I took the screen cap BEFORE I answered.
If you look at the first question (#4) which the answer was year, then look at the second question (#5), year was highlighted and three of the answers from the previous question (#4) was listed along with the answer "A - The First Ten Amendments".