Answer:
A
Explanation:
because B is wrong as it doesn't have the same mass number. C is wrong as it has different number of neutrons. D is wrong as it has more neutrons than protons.
Answer:
25%
Explanation:
Half life means that 50% of the sample is gone at 3.3 years. This means that an additional 3.3 years (total 6.6 years) will reduce the sample a further 50% from the point at 3.3 years. In numbers, this means 50% of 50% (0.50*0.50), which is 25%.
