文章（包括我填对的格子就一并打出来了）Youshouldhavegoodstudyhabits.Thenyoucanspendlesstimebutlearnmore.First,makefulluseofyourtime.Areyourbooksopen?Ifso,pleaseturnoffyourTVandputawayyoursnacks.Ofcour

Question

文章（包括我填对的格子就一并打出来了）
You should have good study habits.Then you can spend less time but learn more.
First,make full use of your time.Are your books open?If so,please turn off your TV and put away your snacks.Of course,you need some time to play.But you should play after study.Remember:Study comes first.
Second,listen to your teachers carefully in your class.You know,it is very important.If you have questions,just ask your teachers.They are very glad to help you.
Third,do your homework by yourself.If you can't work out a problem successfully,you can ask for help.But you can't just copy.Make sure that you u_______ it.
Finally,take a note with you.Sometimes you may have some ideas or questions.Please write them down.Then you can talk to your teachers,parents or friends.
These four tips are helpful to you.Please have a try,my boy!You will succeed if you have good study habits.
画线的地方肯定是填understand没有问题,但是是用什么时态呢?我写的是过去式understood但有同学写的是原形,纠结了.
不是应该确保（说话时已经）懂了吗?

Answer 1

这里的that引导make sure的从句
一般来说,这种从句与make的时态是保持一致的.这里的make是一般现在时,所以从句里的谓语动词understand也用一般现在时.
就make sure 这个词而言,当它用来引导一句虚拟语气的句子,后面的谓语动词就要据情况而定了.