甲和乙两人玩“打弹珠”游戏，甲对乙说：“把你珠子的一半给我，我就有10颗珠子”，乙却说：“只要把你的$\frac{1}{3}$给我，我就有10颗”，如果设乙的弹珠数为x颗，甲的弹珠数为y颗，则列出方程组正确的是（　　）

根据短文理解，从A、B、C、D四个选项中选择最佳答案填空。

    Canada is the second largest 1 in the world. It is over 7,000 kilometres from the 2 coast (海岸）to the east. It 3 six time zones. When it is 9 a.m. in Vancouver on the west coast, it is 1:30 p.m. in St John's on the east coast.

    English and French are the two main 4 in Canada. About 60 percent of its people 5 English, and about 25 percent speak French. More than 70 percent of its population 6 in cities near the US border (边境).

    Ottawa is the capital. Every year millions of tourists go there to 7 museums and take part in the cultural 8. Toronto is the largest city of the country with about 2.5 million people. Montreal is the second biggest French-speaking city in the world.

The maple leaf (枫叶）is the 9 symbol of Canada. The Canadian 10 has a red maple leaf on a red and white background.

图一是探究白磷在水中燃烧的实验装置．该装置的不足之处有：①通过氧气时，白磷易被冲散而较难与氧气接触；②逸散的五氧化二磷会造成空气污染．图二是探究白磷在水中燃烧的改进实验装置，由A、B、C三部分组成．请认真阅读下列内容并回答有关问题：

资料卡：凡能与碱反应生成盐和水的氧化物，称为酸性氧化物．常见的酸性氧化物有CO₂、SO₂、SiO₂、P₂O₅等．