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.
For question 1. Your answer is most likely A.
And for the record. H2O is a compound.
Answer: supernova
Explanation: Massive stars, on the other hand, quickly move beyond these more light elements to create heavier elements like silicon and copper. Anything heavier than iron is created during a supernova–the star-shattering explosion at the end of a massive star's life cycle.
A base provides either hydroxide ions (OH–) or other negatively charged ions that combine with hydrogen ions, reducing their concentration in the solution and thereby raising the pH. In cases where the base releases hydroxide ions, these ions bind to free hydrogen ions, generating new water molecules.
