U.S. stocks rose at Monday's opening, lifted by momentum from merger developments, including China's CNPC International Ltd's $4.18 billion deal to buy PetroKazakhstan Inc. . The Dow Jones Industrial Average was up 20 points at 10,579, the S&P 500 up 2 points at 1,221, and the Nasdaq composite up 6 points at 2,141. Shares of PetroKazakhstan were up almost 20% at $54.33.