The options are flawed.
There is no need to have indicated, in parentheses, whether a respondent identifies as “R,” “D,” or “I.”
Answer to your question: The Democrats, who rigged their 2016 and 2020 U.S. presidential primaries, and other races in between those years, and will likely continue to rig their at least their future presidential primaries, value South Carolina greatly. It serves their desire to get a rightwing candidate to win there with the goal that that candidate will also go on to win the nomination.
In general elections, South Carolina is aligned to the Republicans. It would take carriage of 31 or 32 states, at a minimum, for a winning Democrat to carry South Carolina. (They haven’t carried beyond 28 states since 1996.) The Democrats schedule the state near the front of the primaries schedule to help their abilities to control precisely who ends up with the nomination.