A:将10gNaOH溶解在少量水中,再加蒸馏水直到溶液体积为250ml
B:用托盘天平称量5.85gNaCl固体,配成100ml溶液
C:将常温常压下11.2LHCl气体溶于水,配成500ml溶液
D:将40gNaOH溶解在1L水中
Helen has picked up French and can speak fluently after a short stay with her aunt in Paris.
一个圆环,外圆半径是6厘米,内圆半径是4厘米,圆环面积是____平方厘米。