I answered because "THATS WHY I HAVE A PHONE" but mostly because I'm expecting a call from my daughter in the Air Force, being deployed over seas I never know what my caller ID will be. Anyway, they asked if I voted in the last election and I told them it was none of their business, they asked me to spell my very simple name, I also told them if they knew me they would know how to spell my name and hung up. It's so sad that I can't use my own phone without being blasted with call from God knows who! I hardly ever got a call until I placed my name on the so-called do not call list...!!!
Someone's comment earlier was right on target... if you don't recognize the number, or the caller ID, don't answer the phone. Eventually the robo caller will get the message and stop calling. I did something a year go that has proven quite effective for me. I set my answering machine to come on with my recorded message after just two rights. My messages begins "You have reached (phone number). If you are a telemarketer hang up now." 99% they will hang up instantly, and 95% will stop dialing my number after three unsuccessful attempts. I log every phone number that calls me in my computer and research all that I can. I have managed to stop all the major offenders. May not work for you, but it has for me.