Consider the above trigger intended to assign the Account to the manager of the Account's...

Moving the SOQL query outside the loop prevents it from being executed multiple times, which can lead to hitting governor limits. The last line updating the accountList is indeed needed to save the changes made to the Account records, so removing it is not recommended. Instead, the query should be moved outside the loop and records should be collected in a map for efficiency, which is not one of the provided options. References:

Apex Developer Guide - Best Practices for Apex