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