1a-It would be impossible to send astronauts to the sun because of the extreme heat.
1b-Humans do not yet have the technology to send them to other planets, that’s why it has not been done.
1c.”They” was not specified, so therefore the question cannot be answered. but one possible “they” would be the astronauts on earth there for being ((((1AU from the sun))))
2- 6.727AU
if your teacher does not like those answers maybe he/she should learn how to better word question.