Answer:
Option D
Explanation:
(21C1−10C1)+(21C2−10C2)+(21C3−10C3)+.....+(21C10−10C10)
= (21C1+21C2+....+21C10)−(10C1+10C2+.......+10C10)
= 12(21C1+21C2+.....+21C20)−(210−1)
= 12(21C1+21C2+.....+21C21−1)−(210−1)
= 12(221−2)=220−1−210+1−(210−1)
= 220−210