Positrons are spontaneously emitted from the nuclei of
(1) potassium-37 (3) nitrogen-16
(2) radium-226 (4) thorium-232

Option (1) is the correct answer.

Explanation:

A positron is represent by the symbol .

For example,

The decay reaction is as follows.

The reaction will be as follows.

Therefore, we can conclude that out of the given options positrons are spontaneously emitted from the nuclei of potassium-37.

atomic number of carbon is 6

electronic configuration of carbon is 1s²2s²2p²

orbital diagram of c is as shown here in the image.