Answer: Its option "A" Both A and R are true and R is the correct explanation of A.
Hope it helps
5. A
this is the answer check it out
Answer:
The right answer is "3 g".
Explanation:
Given:
Initial mass substance,

By using the relation between half lives and amount of substances will be:
⇒ 


Thus, the above is the correct answer.
I think the answer might be nuclear physics