【单选题】

One day a little boy comes into a shop and (41) the shop assistant,“I want (42) twelve exercise books of 6 cents each and pencils of 10 cents each. (43) is that altogether ”

The shop assistant writes these numbers down on (44) and thinks for (45) . Then she says,“1 dollar and 62 cents.”“If I gave (46) ten dollars, how much will I get (47) ”“You’ll get (48) for change. Here you are. Here are the things you want.”“ (49) , I don’t want to buy anything.”“ (50) boy looks at the piece of paper and says politely, “This is one of my homework. Thank you very much.Can I take it away ”
“What!”says the shop assistant angrily.
A．a piece of paper
B．some paper
C．a paper