闭环控制系统是使被控量有较高的（）

                                  Some Suggestions on Travel
      Forget about fashion. Always wear your most comfortable clothes when going
on long journey.
     Traveling on trains and buses can be boring, so take a good book to read.
     If you're going somewhere cold, remember to take your warm clothes.
     If you are going somewhere sunny, remember to wear sunblock (防晒霜) and
sunglasses.
     Always take a camera with you to capture those special moments. 
     Be careful with your things whenever you go to busy places, like a train station. There are often thieves there!
     Always leave room in your bag for presents.
     Most countries have lower prices for students, so if you have one, take your
student card with you and save money.