diff --git a/public/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php b/public/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php
index 0033c9bf42..0b73fbb946 100644
--- a/public/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php
+++ b/public/main/exercise/MultipleAnswerTrueFalseDegreeCertainty.php
@@ -501,12 +501,7 @@ class MultipleAnswerTrueFalseDegreeCertainty extends Question
         }
 
         // get the max height of item to have each table the same height if displayed side by side
-        $testCategory = new TestCategory();
         foreach ($scoreList as $categoryId => $scoreListForCategory) {
-            $category = $testCategory->getCategory($categoryId);
-            if ($category) {
-                $categoryQuestionName = $category->name;
-            }
             [$noValue, $height] = self::displayDegreeChartChildren(
                 $scoreListForCategory,
                 300,
@@ -522,12 +517,6 @@ class MultipleAnswerTrueFalseDegreeCertainty extends Question
             }
         }
 
-        if (count($scoreList) > 1) {
-            $boxWidth = $sizeRatio * 300 * 2 + 54;
-        } else {
-            $boxWidth = $sizeRatio * 300 + 54;
-        }
-
         $html = '<div class="row-chart">';
         $html .= '<h4 class="chart-title">'.$title.'</h4>';
 
diff --git a/public/main/exercise/TestCategory.php b/public/main/exercise/TestCategory.php
index 47a188bd52..5320d7bc49 100644
--- a/public/main/exercise/TestCategory.php
+++ b/public/main/exercise/TestCategory.php
@@ -44,7 +44,7 @@ class TestCategory
         $id = (int) $id;
         $courseId = empty($courseId) ? api_get_course_int_id() : (int) $courseId;
         $sql = "SELECT * FROM $table
-                WHERE iid = $id AND c_id = ".$courseId;
+                WHERE iid = $id";
         $res = Database::query($sql);
 
         if (Database::num_rows($res)) {
diff --git a/public/main/exercise/exercise.class.php b/public/main/exercise/exercise.class.php
index e823413997..b1afec2388 100644
--- a/public/main/exercise/exercise.class.php
+++ b/public/main/exercise/exercise.class.php
@@ -3768,17 +3768,16 @@ class Exercise
                         $choice = [];
                         $choiceDegreeCertainty = [];
                         $sql = "SELECT answer
-                            FROM $TBL_TRACK_ATTEMPT
-                            WHERE
-                            exe_id = $exeId AND question_id = $questionId";
+                                FROM $TBL_TRACK_ATTEMPT
+                                WHERE exe_id = $exeId AND question_id = $questionId";
 
                         $result = Database::query($sql);
                         while ($row = Database::fetch_array($result)) {
                             $ind = $row['answer'];
                             $values = explode(':', $ind);
-                            $myAnswerId = $values[0];
-                            $option = $values[1];
-                            $percent = $values[2];
+                            $myAnswerId = $values[0] ?? null;
+                            $option = $values[1] ?? null;
+                            $percent = $values[2] ?? null;
                             $choice[$myAnswerId] = $option;
                             $choiceDegreeCertainty[$myAnswerId] = $percent;
                         }
diff --git a/public/main/exercise/exercise_show.php b/public/main/exercise/exercise_show.php
index 1382c949b2..574601aabb 100644
--- a/public/main/exercise/exercise_show.php
+++ b/public/main/exercise/exercise_show.php
@@ -337,13 +337,11 @@ $sql = "SELECT attempts.question_id, answer
         ON stats_exercises.exe_id = attempts.exe_id
         INNER JOIN $TBL_EXERCISE_QUESTION AS quizz_rel_questions
         ON
-            quizz_rel_questions.quiz_id=stats_exercises.exe_exo_id AND
-            quizz_rel_questions.question_id = attempts.question_id AND
-            quizz_rel_questions.c_id=".api_get_course_int_id()."
+            quizz_rel_questions.quiz_id = stats_exercises.exe_exo_id AND
+            quizz_rel_questions.question_id = attempts.question_id
         INNER JOIN $TBL_QUESTIONS AS questions
         ON
-            questions.iid = quizz_rel_questions.question_id AND
-            questions.c_id = ".api_get_course_int_id()."
+            questions.iid = quizz_rel_questions.question_id
         WHERE
             attempts.exe_id = $id $user_restriction
 		GROUP BY quizz_rel_questions.question_order, attempts.question_id";