B

    Colin Boyle was born in 1973 near Dublin，Ireland. While he was ill in hospital at age 10,his uncle gave him an old violin．He loved it right away．After he left the hospital，he practiced at his school every day after class．

    One day in 1987，John Leaf the manager(经纪人)of several Successful musicians ,came to Colin's school．He was having a meeting with the headmaster when he heard Colin practicing．After the meeting，he found Colin and invited him to appear in one of the concerts he was organizing that yeas Colin，however, refused Leaf's invitation because just then he was preparing for some important school exams．Years later, Colin made it to college to study engineering．At college he met Kim O'Malley, who was studying chemistry(化学)．Kim was also good at music．Being students，they didn't have much money and they usually worked in a restaurant on weekends．

    One evening in April 1992, while Colin and Kim were at work, they heard that there would be no live(现场演出的)music in the restaurant that night because the singer could not come．Colin and Kim persuaded the owner of the restaurant to let them play．Everyone was shocked to hear how good they were．After that, they worked hard together and improved greatly in music．

在催化剂作用下，200mL的某烷烃和某单炔烃的混合气体与H₂加成，最多需要100mL氢气（同温、同压），则混合气体中烷烃与炔烃的物质的量之比为（　　）

若对任意$x\in A,y\in B,\left(A,B\subseteq R\right)$有唯一确定的$f\left(x,y\right)$与之对应，称$f\left(x,y\right)$为关于$x$、$y$的二元函数.现定义满足下列性质的二元函数$f\left(x,y\right)$为关于实数$x$、$y$的广义“距离”:
（1）非负性:$f\left(x,y\right)\ge 0$，当且仅当$x=y=0$时取等号；
（2）对称性:$f\left(x,y\right)=f\left(y,x\right)$；
（3）三角形不等式:$f\left(x,y\right)\le f\left(x,z\right)+f\left(z,y\right)$对任意的实数z均成立.
今给出四个二元函数:①$f\left(x,y\right)=x^2+y^2$；②$f\left(x,y\right)={\left(x-y\right)}^2$；③$f\left(x,y\right)=\sqrt{x-y}$；④$f\left(x,y\right)=\sin \left(x-y\right)$.

能够成为关于的$x$、$y$的广义“距离”的函数的所有序号是（     ）

关于我国土地资源的叙述，正确的是（　　）