Which event takes place first in the stages before the birth of a star?

The contracting cloud is then called a protostar. A protostar is the earliest stage of a star's life. A star is born when the gas and dust from a nebula become so hot that nuclear fusion starts.

Explanation:

the diploid number of chromosomes is sometimes represented by the symbol 2n. for the fruit fly, the diploid number is 8, which can be written as 2n = 8, where n represents twice the number of chromosomes in a sperm or egg cell.