United States Oil ( USO ), the largest ETF trading oil futures, fell 0.0.8%. Oil explorers and producers ETFs led the stock market south Tuesday asFedEx ( FDX ) delivered disappointing first-quarter results and lowered its full-year outlook. Fears of inflation from QE3 and potential supply disruption from conflict in the Middle East has already been priced into the market and now traders are booking profits, DuBord added.