Mr. Green lives in a big city with his wife and two children. One morning Mr. Green takes his new car and washes it when a friend comes. The friend stops and looks at the new car for a minute. Then he asks, "That's a new car. Is it yours? "
"Sometimes." Mr. Green answers.
   The friend is surprised (惊奇). "Sometimes? " he says. "What do you mean?" Mr. Green answers slowly, "Well, when there is a party in town, my daughter Jean drives it. When there is a football, it's my son Jim's turn. When I washes it and it looks very nice and clean, my wife Linda uses it. And when it needs cleaning. It's mine. Choose the correct answer.

实验测定：

①称取一定质量的样品加入稀盐酸中充分溶解，将所得溶液转移至容量瓶并配制成100mL溶液A；

②量取25.00mL溶液A，加入盐酸酸化的BaCl₂溶液至沉淀完全，过滤、洗涤、干燥至恒重，得到白色固体4.66g；

③量取25.00mL溶液A，加入足量KI，用1.000mol•L^﹣1Na₂S₂O₃溶液进行滴定（已知反应为I₂+2Na₂S₂O₃═2NaI+Na₂S₄O₆），消耗30.00mL Na₂S₂O₃溶液至终点．