The answer is all of these occur. The tetrads need to be made before crossing over occurs, which only occurs in prophase 1. That automatically means it has to be all of the above.
I’m not sure if you got the wrong number
Answer:
Brief description of the Orginal experiment state what was done
Explanation:
What did you change?
How did the changes help answer the question
Antibodies are white blood cells that destroy antigens. Antitoxins are white blood cells that destroy toxins(poisons).