Answer:
That is, mechanical waves cannot travel through a vacuum. This feature of mechanical waves is often demonstrated in a Physics class. A ringing bell is placed in a jar and air inside the jar is evacuated. Once air is removed from the jar, the sound of the ringing bell can no longer be heard.
Answer:
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Helium, neon and Xeon belong to the same Column( Group) which is Column 18 or you can say Group 8 in roman numbers
don't forget if you say group you should write in roman numbers okay. Best of luck
Find and Replace dialog box is probably the most useful.