16 neutrons are present in the most abundant isotope.
Explanation:
Phosphorus has 18 isotopes. The most common isotope has mass number (no. of protons 15+ no. of neutrons 16=) 31 .
Relative dating best helps determine fossil age. It's where layers of sedimentary rock and fossils pile up on top of each other; the oldest fossils being in the bottom layer and the youngest in the top.
I don't really know but I pick b.have always been vestigial.
