a graduate student from skokie, illinois... a field application scientist originally from mechanicsburg, pennsylvania... ...whose 2-day cash winnings total... and now here is the guest host of "jeopardy!"-- katie couric. [ applause ] hi, everyone, and thank you, johnny gilbert. welcome to "jeopardy!" this has been an extraordinary experience for me. and on a personal note, it has made me respect alex trebek even more than i already did. hosting this show is hard, and the fact that he did this while he was fighting pancreatic cancer, well, that was downright herculean. i am so proud to help carry on his legacy and raise money for pancreatic cancer research. so, dave, kathleen, tom, you ready to do this thing? you win big, "jeopardy!" matches your winnings and gives it to pancreatic cancer research. so let's get started, shall we, with our first round of "jeopardy!" the categories are... dave, you're up. the squad for $400. - dave. - what is the bomb squad?