设有如下语句序列: CREATE PROCEDURE sp_mathop(IN a INT, IN b INT) BEGIN SET @var1 = 1; SET @var2 = 2; SELECT @sum:=(a + b) AS sum, @dif:=(a - b) AS dif; END; CALL sp_mathop (3, 4); SELECT @a, @var1, @var2, @sum, @dif; 关于上述语句中变量使用的叙述中,正确的是
【单选题】Propanone has the molecular formula C3H6O.The enthalpy change of combustion of hydrogen is –286kJmol–1;The enthalpy change of combustion of carbon is –394kJ mol–1The enthalpy change of combustion of c...