Correct Option: D

²⁰⁰X₉₀ → ¹⁶⁸Y₈₀.
We know that
²⁰⁰X₉₀ → n₂He⁴ + m_{- 1}β⁰ + ¹⁶⁸Y₈₀.
Therefore, in this process,
200 = 4n + 168

or n =	200 - 168	= 8.
	4

Also, 90 = 2n – m + 80
​or, m = 2n + 80 – 90 = (2 × 8 + 80 – 90) = 6. ​
Thus,  respective number of α and β-particles will be 8 and 6.