diff --git a/4a1s/CP/PL - Aula 7.md b/4a1s/CP/PL - Aula 7.md
index 0d48f9d..4c9f03a 100644
--- a/4a1s/CP/PL - Aula 7.md	
+++ b/4a1s/CP/PL - Aula 7.md	
@@ -588,4 +588,5 @@ We can change the code to:
 And the results will always be:
 
 ### d)
-We can use _reduction_ to do that.
\ No newline at end of file
+We can use _reduction_ to do that (and it's more efficient than 'critical').
+