In some languages, such as French and Spanish, it's ungrammatical or at least uncommon to use possessive pronouns to refer to parts of the body in some contexts: People say "the head," "the face" to refer to their own face, at least in some circumstances or kinds of constructions. But when the noun as an object is not a body part, possessive pronouns are ungrammatical or strange, at least in many cases.
It seems that English might have different grammar in this respect. I don't know what rules dictate the use of a definite article OR a possessive pronoun in my sentence but my intuition is B is more correct. I don't know why. Can anyone tell me whether A is also acceptable and if not, why only B is right?
A. In his dissertation on biodiversity submitted yesterday, John explored ... (extraneous information omitted)
B. In the dissertation on biodiversity submitted yesterday, ...