Correct Option: D

As we know that
7¹ = 7;
7² = 49;
7³ = 343;
7⁴ = 2401 ;
7⁵ = 16807
i.e. The unit’s digit repeats itself after power 4.
Remainder after we divide 245 by 4 = 1
∴ Unit’s digit in the product of (4387)²⁴⁵ × (621)⁷² = Unit’s digit of (4387)²⁴⁵ × Unit digit of (621)⁷²
(621)⁷² = Unit’s digit of (7)²⁴⁵ × Unit digit of (1)⁷²
(621)⁷² = Unit’s digit of (7)¹ × Unit digit of (1)⁷²
∴ Unit’s digit in the product of (4387)²⁴⁵ × (621)⁷² = 7 × 1 = 7