Which word equation represents ${\beta ^ + }$ decay?
A. ${\rm{Proton}} \to {\rm{neutron}} + {\rm{electron}} + {\rm{electron\,antineutrino}}$
B. ${\rm{Proton}} \to {\rm{neutron}} + {\rm{electron}} + {\rm{electron\,neutrino}}$
C. ${\rm{Proton}} \to {\rm{neutron}} + {\rm{positron}} + {\rm{electron\,antineutrino}}$
D. ${\rm{Proton}} \to {\rm{neutron}} + {\rm{positron}} + {\rm{electron\, neutrino}}$

Hint:Beta decay is a form of radioactive decay and beta positive decay is one of the types of beta decay in which proton in the nucleus of a radioactive sample disintegrates into neutron or vice-versa.

Complete answer:
-The process of beta decay is done in such a way that the ratio of proton and neutron is optimum. In the process of achieving optimum ratio a beta particle is emitted from the nucleus, this emitted beta particle could be positive or negative. Hence, beta decay is classified into two categories; ${\beta ^ + }$ decay or positron emission and electron mission.
-The proton of the radioactive sample is converted into a neutron which releases a positron and an electron neutrino. This positron is a positive particle, and its mass is the same as an ordinary electron, but it has the opposite charge. For a positron emission mass number is the same but the atomic number decreases by one as a result of which it forms a difference.
-Hence, in positron emission a daughter nucleus is produced which has the atomic number one less than the parent nucleus and the mass number is the same. Thus, the equation can be written as:

${\rm{Proton}} \to {\rm{neutron}} + {\rm{positron}} + {\rm{electron\,neutrino}}$

Therefore, Option (D) is the correct answer.

Note:Do not get confused between beta positive decay and beta negative decay because $\beta $ only represent the emission of electrons from nuclei but this electron emission could be positively charged or negatively charged.