题目

In 2004, the number of students in our school ________ 5,000. A. is              B. are                   C. was                 D. were 答案：C7．下列实验现象描述不正确的是（　　）A．红磷在空气中燃烧产生大量白烟B．硫在氧气中燃烧产生苍白色火焰C．铁丝在氧气中剧烈燃烧，火星四射D．氢气在空气中燃烧发出淡蓝色火焰