完成句子。根据括号内汉语提示，完成句子。
(1)It's too dangerous to (游泳)____ alone.
(2)Jack is the (高)____ of the five boys.
(3)What would you do if your brother borrowed your bike without ____ （允许）.
(4)Sandy enjoys reading books and she has been to many (图书馆)____ .
(5)Don't forget to check your test paper (仔细)____ before the exam is over.
(6)If you stand very close to the Europeans you are talking with,some might feel____ （不自然，不舒服）.
