Answer
Please see the work below.
Work Step by Step
We know that
a. Positron emission or electron capture
$(\frac{N}{Z}=\frac{30}{30}=1)$
b. Positron emission
$(\frac{N}{Z}=\frac{4}{6}<1$ and $Z<20)$
c. $\alpha$ emission $Z>83$
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