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Option (4) 25%

income = Rs.100
Initial saving = Rs.20
New Income = Rs.120
Income after donating to charity = Rs.108
Saving now = Rs.18
Initial Saving Percent = 20%
New Saving Percent =18/120 × 100 = 15%
Change in 'Saving Percent' = 5/20 × 100 = 25%

:)