Hydrogen, oxygen and nitrogen are counted as some most important elements and found abundantly. About 75% of this universe is composed of hydrogen and helps different other matters to sustain. Large starts and planets, electrons and protons are also composed of hydrogen.
A sheet tab appears at the bottom of your worksheet. It has the name of the worksheet on it, which can be changed and you can also change its colour. This can be done by right clicking on it and picking the option from the shortcut menu that appears. By clicking a sheet tab, you can make that sheet the active sheet so that you can work on it.
In order to hide a worksheet or tab in Excel, right-click on the tab and choose Hide. That was pretty straightforward. Once hidden, you can right-click on a visible sheet and select Unhide. All hidden sheets will be shown in a list and you can select the one you want to unhide.