：‌已知一个运算被定义为(define (firstCalc x) (* x x))，在其基础上进一步定义新运算secondCalc为x2+y2+z2，下列运算组合式书写正确的是_____。​A: (define secondCalc (+ (firstCalc x) (firstCalc y) (firstCalc z)))B: (define (secondCalc x y z) (+ firstCalc x y z))C: (define (secondCalc x y z) (+ (firstCalc x) (firstCalc y) (firstCalc z)))D: (define secondCalc x y z (+ (firstCalc x) (firstCalc y) (firstCalc z)))答案: (define (secondCalc x y z) (+ (firstCalc x) (firstCalc y) (firstCalc z)))19、