Physics is more difficult and requires excellent computing power. It is puzzling that the calculation score is often greater than the relational expression, and some special methods will be used, but it is often unexpected because it is within the ability of high school students, so divergent thinking is needed.
Chemistry is not clear, but it is relatively simple knowledge in college, with emphasis on learning and acceptance.
Biology is relatively simple, but it requires both fine knowledge and extensive knowledge (very extensive), which is often different from textbooks and has many multiple-choice questions.
It's best not to stick to this, make sure you still have spare capacity, and it's best to start training in the first year of high school, even if you don't win the prize.