diff --git a/README.md b/README.md
index a3a32bc2..ec9422d0 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
 # learn-js
 JavaScript tutorial repo
 
-### REPLACE WITH YOUR FULL NAME
+### Yuanyuan Yang
diff --git a/quiz/exception.html b/quiz/exception.html
index c154b213..a01e0d2c 100644
--- a/quiz/exception.html
+++ b/quiz/exception.html
@@ -24,8 +24,16 @@ <h1>Error Handling with Array Map</h1>
       // Using map to calculate the square root of each number
       // Use Math.sqrt(number) to calculate sq root
       const squareRoots = numbers.map(number => {
-        return 0
-    });
+        try {
+          if (number < 0) {
+            throw new Error(`Cannot calculate square root of negative number: ${number}`);
+          }
+          return Math.sqrt(number);
+        } catch (error) {
+          console.error(error.message);
+          return NaN;
+        }
+      });
 
       // Displaying the original and transformed arrays
       console.log('Original Numbers Array:', numbers);
diff --git a/quiz/scripts/map-deep.js b/quiz/scripts/map-deep.js
index e97665e5..8635a723 100644
--- a/quiz/scripts/map-deep.js
+++ b/quiz/scripts/map-deep.js
@@ -6,7 +6,7 @@ const originalMatrix = [
   ];
   
   const newMatrix = originalMatrix.map((row) => {
-    return row.sort();
+    return [...row].sort((a, b) => a - b);
   });
   
   // Modifying the original matrix (changing the last element of the first row)
@@ -15,4 +15,4 @@ const originalMatrix = [
   // Displaying the original and new matrices
   console.log('Original Matrix (modified):', originalMatrix);
   console.log('New Matrix (unaffected):', newMatrix);
-  
\ No newline at end of file
+  
diff --git a/quiz/scripts/stack-q1.js b/quiz/scripts/stack-q1.js
index 0d719223..40fd495e 100644
--- a/quiz/scripts/stack-q1.js
+++ b/quiz/scripts/stack-q1.js
@@ -9,6 +9,14 @@ class PStack {
     return this.#id;
   }
 
+  get persons() {
+    return this._persons.slice();
+  }
+
+  addPerson(person) {
+    this._persons.push(person);
+  }
+
 }
 
 class PStackImpl extends PStack {
@@ -21,6 +29,10 @@ class PStackImpl extends PStack {
   }
 
   pop() {
+    if (this.persons.length === 0) {
+      console.error('No persons to pop.');
+      return NaN;
+    }
     return this._persons.pop().age
   }
 }