Here's the answer:
“お好きな浴衣を選んでください”
(o suki na yukata o eran-de kudasai)
Watch a real native speaker say it:
Here's how it sounds in a textbook:
You could also say:
- 好きな浴衣を選んでください
Fun fact: the hundreds of thousands of people learning Japanese with Memrise get this phrase correct 92.09% of the time!
