Rewrite the following sentences as required. （按要求改写下列句子）
He has already bought many oranges.（改为一般疑问句）
________ he bought many oranges ________?
Many students have classes at weekends. （改为否定句）
Many students __________ __________ classes at weekends.
I’d like to be a doctor because I want to make sick people better. (对划线部分提问)
_________ ________ you like to be a doctor?
I leave home at 7:30 every day. I get to school at 7:45.（保持原句意思）
It ________ ________ fifteen minutes to get to school every day.
Tom’s diet is healthy. Jack’s diet is not very healthy.（保持原句意思）
Jack’s diet is ________ ________ than Tom’s diet.