下列关于燃烧现象的描述中,正确的是 ( )
A:铁丝在氧气中剧烈燃烧,火星四射
B:红磷在空气中燃烧产生大量白色烟雾
C:硫在氧气中燃烧发出淡蓝色火焰
D:碳在氧气中燃烧生成二氧化碳
陇海线与京广线交会的铁路枢纽是 ( )
若3x=12,3y=4,则3x﹣y=____ .
例:A:Jenny often walks to school.
B:Jenny walked to school yesterday.
C:Jenny is going to walk to school tomorrow.