The optimization process and recommendations:

1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
2. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.

Optimal indexes for this query:

CREATE INDEX itemchoicestable_idx_itembankid ON OdeaMainDataBase.dbo.ItemChoicesTable (ItemBankID);
CREATE INDEX studenttesttablefr_idx_studid_examid_itemban_choicei ON StudentTestTablefromRemark (StudID,ExamID,ItemBankID,ChoiceID);

The optimized query:

SELECT
        OdeaMainDataBase.dbo.ItemChoicesTable.*,
        CASE 
            WHEN EXISTS (SELECT
                * 
            FROM
                StudentTestTablefromRemark 
            WHERE
                StudentTestTablefromRemark.StudID = @studId 
                AND StudentTestTablefromRemark.ExamID = @examId 
                AND StudentTestTablefromRemark.ItemBankID = @itemBankId 
                AND StudentTestTablefromRemark.ChoiceID = OdeaMainDataBase.dbo.ItemChoicesTable.ChoiceID) THEN 'True' 
            ELSE 'False' END AS isAnswered 
FROM
OdeaMainDataBase.dbo.ItemChoicesTable 
WHERE
OdeaMainDataBase.dbo.ItemChoicesTable.ItemBankID = @itemBankId