The Common category includes the following blocks: Paragraph, image, headings, list, gallery, quote, audio, cover, video. The paragraph block is the default block type.  It should not have any alignment...

This post tests various embed blocks:

Really cool to read through and find so much awesomeness added to WordPress 3.6 while I was gone. I should take three weeks off more often. — Andrew Nacin (@nacin)...

Posted as per the instructions in the Codex.

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