The Em Dash

Choose the answer that uses em dashes correctly in the sentence.
The only thing Felix could do if he could do anything was to sit and wait for the results

• The only thing Felix could do if he could do anything-- was to sit and wait for the results.
• The only thing Felix could do if he could do anything was to sit and wait for the results.
• The only thing Felix could do-- if he could do anything-- was to sit and wait for the results
• The only thing-- Felix --could do if he could do anything was to sit and wait for the results.

Which is the correct way to use the dash in the following sentence: The Beatles (the most famous rock band in history) were from England.

• The Beatles, the most famous rock band in history-- were from England.
• The Beatles-- the most famous rock band in history-- were from England.
• The Beatles - the most famous rock band in history; were from England.
• The Beatles-- the most famous rock band-- in history were from England.

After which word should an em dash be added in this sentence:
It’s not only our lives on the line it’s the lives of thousands of Allied soldiers.

• not
• only
• line
• Allied

After which word should an em dash be added in this sentence: 
The old man realized it was finally time to revisit the land of his youth Ireland.

• revisit
• realized
• man
• youth

After which word should an em dash be added in this sentence: Books, paper, pencils many students lacked the most basic classroom materials in nineteenth-century America.

• lacked
• basic
• pencils
• students