参军是enter the army还是enter into the army

参军是enter the army还是enter into the army 一般来讲是join the army 还是 join army 还是join an army 是enter the cave 还是enter into the cave enter for与enter的区别?enter for与enter有什么区别?是说enter the exam 还是enter for the exam before you e---- the house 用enter 还是entered 是join the army（陆军）还是take part in army（陆军）? 我弟弟还未到参军的年龄 My brother is ( ) young ( ) ( ) the army 英语 自他参军至今已有十年了. It is ten years --- he --- the army enter,join,take part in区别enter the army=join the army 为什么?enter a contest=take part in a contest 请问为什么？ 按回车键是press the enter button 还是press the enter key 是join in army还是 join in a army? 改错He wants to enter the army when he grows up. 现在完成时 自他参军至今已有十年了.It is ten years since he jioned the army.since前为什么不用现在完成时。 Jim isn't old e() to join the army.(军队) （选择正确的词填空,使短文完整） A young man was going to join the army(参军)and had to take 等等（选择正确的词填空,使短文完整）A young man was going to join the army(参军)and had to take medical examination(体格 it has been 5 years since he joined the army 是表肯定还是否定呢 求教英语大神详解 all the students in my class are working hard and doing what they can___a good university.是填enter还是to enter为什么 参加比赛 英语怎么说是enter the competition还是 enter for the competition?thanks