The first-level differences are 15, 25, 35 and 45. These differences themselves form an arithmetic progression with common difference 10. Thus the next difference should be 55. When 55 is added to the last term 128, we obtain 183, which continues the pattern at both the term level and the difference level.
Option A:
Option A gives 178, which would create a difference of 50 from 128. This would make the sequence of differences 15, 25, 35, 45, 50, where the last increase is 5 rather than 10. Hence 178 breaks the structure of the second-level arithmetic progression.
Option B:
Option B gives 188, corresponding to a difference of 60 from 128. That would yield differences 15, 25, 35, 45, 60, causing the final increment to jump by 15 instead of 10. Therefore 188 does not preserve the consistent behaviour among the gaps.
Option C:
Option C gives 183, leading to a difference of 55 from 128. The differences become 15, 25, 35, 45, 55, a clear arithmetic progression with constant step 10. This perfect alignment with the observed pattern makes 183 the correct next term.
Option D:
Option D gives 193, implying a difference of 65 from 128. This creates an irregular spike in the differences and abandons the neat step of 10 between them. Consequently, 193 is not a valid continuation of the series.
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