Read this and answer the question. If the question is unanswerable, say "unanswerable".

With the continuing controversy that had surrounded the military service of George W. Bush since the 2000 Presidential election (when he was accused of having used his father's political influence to gain entrance to the Texas Air National Guard, thereby protecting himself from conscription into the United States Army, and possible service in the Vietnam War), John Kerry's contrasting status as a decorated Vietnam War veteran posed a problem for Bush's re-election campaign, which Republicans sought to counter by calling Kerry's war record into question. As the presidential campaign of 2004 developed, approximately 250 members of a group called Swift Boat Veterans for Truth (SBVT, later renamed Swift Vets and POWs for Truth) opposed Kerry's campaign. The group held press conferences, ran ads and endorsed a book questioning Kerry's service record and his military awards. The group included several members of Kerry's unit, such as Larry Thurlow, who commanded a swift boat alongside of Kerry's, and Stephen Gardner, who served on Kerry's boat. The campaign inspired the widely used political pejorative 'swiftboating', to describe an unfair or untrue political attack. Most of Kerry's former crewmates have stated that SBVT's allegations are false.

What military branch was George W. Bush in?
the Texas Air National Guard