阅读短文，下列问题
B
The plane took off. A passenger needed a cup of water to take his medicine. An air hostess(空姐) told him that she would bring him the water soon. But the air hostess was so busy that she forgot to bring him the water. As a result, the passenger couldn't take his medicine on time. About half an hour later, she hurried over to him with a cup of water, but he refused it.
In the following hours, each time she passed by the passenger, she would ask him with a smile whether he needed help or not. But the passenger never paid notice to her.
When it was time to get off the plane, the passenger asked her to hand him the passengers' booklet(留言簿), she was very sad. She thought that he would write down bad words in it, but with a smile she handed it to him.
Off the plane, she opened the booklet and then smiled. The passenger put it, “In the past few hours, you have asked me whether I needed help or not for twelve times in all. How can I refuse your twelve faithful(真诚的) smiles?”
从左往右数，第十个同学应报什么数?