Question

which of the following decay(s) will definitely takes place when n/p ratio for a radioactive nuclei lies below the stability belt
(A) k electron capture
(B) both a and b
(c) alpha decay
(d) positron decay
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Answer 1

When n/p ratio is low, it needs to be increased. This can be done by increasing the number of neutrons or decreasing number of protons.

So it has to emit positron (decreasing number of protons) i.e positron decay.