Must the senior high school entrance examination be a 0.5 black pen?

You can confirm it again carefully. There is no such provision in the senior high school entrance examination and there is no such provision in the college entrance examination. I think it's for you to write with this pen, so that your handwriting is thicker and easier to mark. In the senior high school entrance examination, because there are too many papers, the marking teacher will not feel very good about those weak handwriting, so he will lower the scores he should have. It is estimated that your teacher made you do this out of this psychology. In short, as long as the handwriting is clear, there will be no problem.