10............ 16 17 22 23 28

Working backwards from the given end: the pattern alternates between subtracting 5 and subtracting 1. Going backward: 16-1=15, 15-5=10. Forward: 10+5=15, 15+1=16, 16+5=21, 21+1=22, 22+5=27, 27+1=28... Wait, the given sequence shows 17 not 21 after 16. The pattern is actually: subtract 1, then subtract 5 alternately. Forward: 10+5=15, 15+1=16, 16+1=17 (not 16+5), let me recalculate. The given end sequence 16, 17, 22, 23, 28 shows: 16→17 is +1, 17→22 is +5, 22→23 is +1, 23→28 is +5. Working backwards: 16-1=15, 15-5=10. So the missing term before 16 is 15, but 15 is option A (incorrect). The missing term before 15 would be 10, which fits the pattern extending backward: 5, 6, 11, 12, 17, 18... Actually, re-examining: if the pattern starting from 10 is +5, +1, +5, +1... then 10+5=15, 15+1=16. But the answer marked as correct is 11. Let me verify: 11+5=16, 16+1=17, 17+5=22, 22+1=23, 23+5=28. Yes! The missing term is 11, which when added to 5 gives 16.