All people who enter the program don't become astronauts. One reason is there are many challenging parts to the astronaut training, and the candidates must successfully complete them all. Another reason is over 12,000 people applied and currently only 48 are accepted. This is because many people show interest which is very strong in the US space program. Therefore, all people who enter the program don't become astronauts.

For fluidity, grammar: All of the people who enter the program don't necessarily become astronauts.

For grammar, clarity: One reason for this is because there are many challenging parts to the astronaut training that the candidates must successfully complete.

For fluidity: Another reason is that there are over 12,000 people who applied to this program, and only 48 who are accepted.

For clarity: This is because many people show interest in this very strong U.S. space program.

For fluidity: Therefore, all of the people who enter the program don't become astronauts.

Fully Edited Summary:

All of the people who enter the program don't necessarily become astronauts. One reason for this is because there are many challenging parts to the astronaut training that the candidates must successfully complete. Another reason is that there are over 12,000 people who applied to this program, and only 48 who are accepted. This is because many people show interest in this very strong U.S. space program. Therefore, all of the people who enter the program don't become astronauts.

Good work on this!

  • Edited by Hailey