Answer:
The answer to your question is letter B.
Step-by-step explanation:
Data
Polonium-208 half-life = 2.9 years
Original sample = 2 mg
Total time = 8 years
Process
Mass Time
2 mg 0 years
1 mg 2.9 years
0.5 mg 5.8 years
0.25 mg 8.7 years
The mass of sample must be between 0.5 and 0.25 mg, from the options given the only possible answer is letter B 0.296 mg