Answer: Option (c) is the correct answer.
Explanation:
A positron is denoted as 
, a neutron is denoted as 
, an electron is denoted as 
, and a proton is denoted as 
.
Therefore, when 
will decay into 
this means there occurs decrease in its mass number. Hence, it means a neutron will be releasing during this reaction.
The reaction will be as follows.
Answer:
Rock Y
Explanation:
The rock that is older shall be determined based on the number of half lives it has witnessed. A half life is simply the amount of time required for a sample to decay to half of its original mass.
Rock X
From 100% uranium, it decays to 50% uranium. This means it went through just one half life.
Rock Y
From 100% uranium to 25% uranium
100 --> 50 (first half life)
50 --> 25 (second half life)
This means it wen through 2 half lives.
Rock Y is older than Rock X
Answer:
A-20 B-40 C-Ca D-10 E-9 F-F
