CREATE TABLE table_19890 ("Series Ep." TEXT, "Episode" FLOAT, "Netflix" TEXT, "Segment A" TEXT, "Segment B" TEXT, "Segment C" TEXT, "Segment D" TEXT)

What was segment C when segment D was fluorescent tubes?
SELECT "Segment C" FROM table_19890 WHERE "Segment D" = 'Fluorescent Tubes'
SELECT "Segment C" FROM "table_19890" WHERE "Segment D" = 'Fluorescent Tubes'