Step 1: Subject-verb agreement
“Each” is singular, so the verb should be singular: “has submitted”.
Step 2: Analyze pronoun
Though “their” is plural, it is often used for singular indefinite pronouns in modern English for gender neutrality.
Step 3: Error is in verb “have submitted”
It should be “has submitted”.
The scientist's theory was initially met with _________, but later gained widespread acclaim after consistent experimental validation.