Parents, would you be mad with your child getting a 'B' in school?

Hi, I got a grade “B” for maths and English for this semester, and my parents are really upset. I don’t understand why my teacher gave me a B for English, as she mainly based this grade on a piece we had to do that included: report, narrative, diagram, poem and facts, and the invention had to be unique. We had free choice of anything invented in the 21st century. Most of the class, around 25 of 30 students, did a version of iPhone. I did Toyota’s hybrid car, 2 of the boys did an airplane (not sure which one), my friend did the artificial heart, and someone did a vacuum cleaner. She gave the grades as follows: me – A, my friend – A, vacuum – B, plane – A and B iPhone – from A to A++. Why? Does anyone know?
On maths, I had sprained my foot just below the ankle and it got swollen, I couldn’t walk properly for a week. I missed out on crucial work, which meant a lot of errors in my test, and the teacher, even though she knew why I didn’t learn it, didn’t let me retake the test, after I said I had spent the few nights learning the topics. My parents are so angry I got a B! What to do?