I'd say that the precautions that you should follow to prevent an abrasive wheel from cracking is A. all of the answers are correct: fit the wheel on the spindle, make sure the spindle speed does not exceed the maximum speed marked on the wheel, and tighten the spindle nut enough to hold the wheel in place without distorting the flange.
Log in is the feature that allows you to access your electronic account in a website, database or other, also a bank account. Your username and password are stored in cookies (files that websites use and are stored in your browser) for the session. This is true if we talk about websites.
When you're done, you log out from your account, you disconnect. Cookies are cleared (for websites) and you're out.
They both do the same thing.
Answer: The answer is true
They have a sound package. More info here: https://atom.io/packages/sound