The Isotope Is Unstable $\neq$ 1
B) N/Z Is Relatively Low and Z < 20

The isotope is unstable. This is predictable because

A) N/Z $\neq$ 1.
B) N/Z is relatively low and Z < 20.
C) N/Z is relatively large and Z < 20.
D) Z is small.
E) N is large.