题干

下列实验基本操作不规范的是(   )

A:点燃氢气之前必须检验氢气的纯度

B:使用胶头滴管时,应使滴管始终垂直向下,一般不得伸入容器内

C:用酒精灯给烧瓶中的液体加热时,无须垫石棉网

D:使用托盘天平称量物质时,应先将游码拨到刻度尺最左端,然后调节螺母将天平调平衡

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答案(点此获取答案解析)

C

同类题2

阅读下面的文字,完成下列小题。

                                                                                    清晨我漫步在山坡谷地,

                                                                                    晨光宣泄着永恒的秘密,

                                                                                    山涧里流倘出一条小溪,

                                                                                    她在歌、在唤、在吐露心曲


                                                                                    生活并非安逸,

                                                                                    它是思念和希冀。

                                                                                    死亡并非哀歌,

                                                                                    它是失望与憔悴。

                                                                                    智者不在言词,

                                                                                    其秘密在言词背后藏nì。

                                                                                    伟人不在高位,

                                                                                    不屑权位者才配享荣誉。

                                                                                   (纪伯伦《小溪,你说什么》节选)