The digit in the unit's place of [(251)98 + (21)29 - (106)100 + (705)35 - 164 + 259] is :

Answer: Option B

Unit digit in [(251)⁹⁸ + (21)²⁹ - (106)¹⁰⁰ + (705)³⁵ - 16⁴ + 259]
= unit digit in (1 + 1 - 6 + 5 - 6 + 9)
= 4