Concept:The sequence follows a fixed pattern: divide by 2, then square the result, then add 5.Explanation:For 10−5−25−30:10÷2=55×5=2525+5=30For 4−2−4−9:4÷2=22×2=44+5=9Check the options using the same operations:Option A: 7÷2=3.5î€ =49, so it does not follow.Option B: 8÷2=4, 4×4=16, 16+5=21 — this follows correctly.Option C: 12÷2=6, 6×6=36, but 36+5=41î€ =40, so it does not follow.Option D: 10÷2=5î€ =20, so it does not follow.Answer:Option B: 8−4−16−21.