--- a/hws/hw04.tex	Thu Oct 19 11:04:43 2017 +0100
+++ b/hws/hw04.tex	Thu Oct 19 13:15:22 2017 +0100
@@ -11,7 +11,7 @@
 \begin{enumerate}
 
 \item If a regular expression $r$ does not contain any occurrence of $\ZERO$,  
-is it possible for $L(r)$ to be empty?
+is it possible for $L(r)$ to be empty? Explain why, or give a proof.
 
 \item Define the tokens and regular expressions for a language
   consisting of numbers, left-parenthesis $($, right-parenthesis $)$,