diff --git a/labs/07_list_implementation/README.md b/labs/07_list_implementation/README.md
index cb1c90f..ffe4198 100644
--- a/labs/07_list_implementation/README.md
+++ b/labs/07_list_implementation/README.md
@@ -54,6 +54,8 @@ $ ./a.out
 
 **To complete this checkpoint**, explain to a TA your implementation and show the output of your program.
 
+<!--TODO: how about memory leaks?-->
+
 <!--## Checkpoint 3: Debugging a Merge Sort program. 
 *estimate: 30-40 minutes*
 
diff --git a/labs/07_list_implementation/checkpoint3.cpp b/labs/07_list_implementation/checkpoint3.cpp
index 2fc1e85..6474b38 100644
--- a/labs/07_list_implementation/checkpoint3.cpp
+++ b/labs/07_list_implementation/checkpoint3.cpp
@@ -12,6 +12,7 @@ public:
 };
 
 // function to merge two sorted doubly linked lists
+// this function returns a pointer pointing to the head node of the merged list.
 template <class T>
 Node<T>* mergeLists(Node<T>* head_A, Node<T>* head_B) {
 }