My pick is A

Schliemann determined at the age of seven to find the site of ancient Troy and devoted his subsequent career to do it.
A. devoted his subsequent career to do it
determined and devoted are in the same tense.
Also his clearly pointing to Schliemann and it is pointing to work/task( to find the site of ancient Troy)

I think its B. From what I can tell, "it" in choice A has no clear antecedent

IMO A - Is the correct answer.

What is OA?

５． Schliemann determined at the age of seven to find the site of ancient Troy and devoted his subsequent career to do it.

A. devoted his subsequent career to do it
B. has devoted his subsequent career to do that
C. devoted his subsequent career to such an end
D. has devoted his subsequent career for that
E. devoted his subsequent career to that end

Either this question is incorrectly worded here or this is a very poor quality question!

In the main stem a comma/had/was is missing after Schielmann and that would change the answer choices otherwise in the present construction what we get is a non sensical sentence.

What is the source, OA and explanation. Before you put up the OA please check if you have typed the question correctly

My guess is a comma is missing after Schielmann and after Troy... if that is the case then my answer would be E