Do you think that this unfair?

I am in an honors cl in high school. My teacher wrote on the board "read section one and two and complete corresponding sections in packet." She then read out-loud to the cl "read section one and two and complete corresponding sections in packet." I read and filled out those two sections in the packet. I checked her online page and it said to complete the packet. I thought that this must be a mistake since she said that what she says in cl triumphs over the online page. I only did the two sections. The next day 5 out of 20 kids completed the packet. She gave everyone including me a 0 for the homework ignment. I told her that she wrote only sections one and two on the board but she said that I was lying and walked away. The other kids don't care since they have A's but I have a B+ and I am trying so hard to get it to an A- but this brings me down to a B.