The answer is option 2, ‘his’.
Singapore uses British English, and ‘everyone’ is an indefinite pronoun, so with reference to the Cambridge Dictionary:
‘When we want to refer back to everyone or everybody and we don’t know if everyone is male or female, we use him or her and his or her. In informal styles, we use plural pronouns they, their and them.’ (https://dictionary.cambridge.org/grammar/british-grammar/everyone-everybody-everything-everywhere)
This grammar rule helps us narrow down the answer to either ‘his’ or ‘her’.
Between ‘his’ and ‘her’, we will choose ‘his’ as it is common practice to use a singular male pronoun to follow indefinite pronouns. Also, when referring to general observations, facts or broadly inclusive statements, the male pronoun ‘he’/’his’ is often used.