My question to stop spam

Yesterday I installed the textual confirmation modification for my phpBB discussion forums. With the installation was a couple of questions that I could use or I could make up my own questions. The questions people registering for my discussion forums had to answer was this; are you a human or say hello. Both were kind of easy and a little stupid. So I made up my own question and I have just saved it. The question is this; Name the most popular search engine. The answer is Google (I hope that I am right on this one). Hopefully this isn´t too hard for most people, I hate for people not to be able to register because of failing to answer the question. So far, the modification has prevented about 10 people / bots from registering.