根据短文选择答案。

Sam lives in New York City. His father has a shop there, and his mother is a teacher. He is seven years old now and begins to go to school this autumn. The school is a little far from their shop, so his father drives him to school every day. He is never late for school and his teachers like him. It's Monday today. Miss Hunt is teaching the students to count(数数) from one to ten. Sam studies hard. Soon he can count them. Miss Hunt is happy and asks, “How many people are there in your family, Sam?” Sam stands up and begins to count with his fingers. Then he says, “Two, Miss Hunt.”“Who are they?”“My father and mother.” “Oh,”Miss Hunt is surprised and says, “There are three people in your family!”“But now I’m not at home. I'm at school, you know!”

下列有关文学常识及课文内容的表述，有错误的一项是（   ）。

有碳酸镁与氧化镁的混合物共重12.4克，把该混合物加入到192克稀盐酸中恰好完全反应，称得反应后溶液的质量为200克．试计算反应后所得溶液中溶质的质量分数．（写出具体计算过程）

南瓜的扁盘形、圆形、长圆形三种瓜形由两对等位基因控制（A、a和B、b），这两对基因独立遗传．现将2株圆形南瓜植株进行杂交，F₁收获的全是扁盘形南瓜；F₁自交，F₂获得137株扁盘形、89株圆形、15株长圆形南瓜．据此推断，亲代圆形南瓜植株的基因型分别是（　　）