关于原句改定语从句或状语从句

because the professor is devoted to his work,he cares little about any other things
when he is dressed in a white uniform,he looks more like a cook than a doctor
because kate was worn out for a long walk,Kate called and said she couldn't come to the party.
because/when the balloon was freed of the barden of ice,it climbed up and drifted away
alough Vietnam is once condered to be a a difficult and even dangerous place,it is now a friendly destination that welcomes vistors from all over the world.
though the two girls were told to stop.they kept on talking at the meeting.
once such a chance was lost,it might never come again
as your composition is written carelessly ,it is full of mistakes