I think an astronaut, an architect and movie director are difficult.
Because an astronaut is hard to go space and an architect is hard to make a building. And a movie director is hard to make a movie.

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 You can also say that:

      I think the hardest jobs are: astronaut, architect and movie director.

~Going to space is hard and dangerous for Astronauts.

~ Making buildings are also hard. Architects need to be creative.

~ It is not also easy to make movies.  Movie directors should make the people love the movie.

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Hello Eric!

           All jobs are not easy, but it will if you love what you are doing. ^^

Thank you for making your homework. I really appreciate your effort. You can make your own homework just base on your idea. Great job!

Keep up the good work, Eric. Always aim high!

~Teacher Cassie