If you keep your mind clear,you will memorise things well.(这里if就是如果不是虚拟语气)
If you have kept your mind clear,you would memorise things well.(这是虚拟语气,意思就是那人一定忘记了什么)
If you keep your mind clear,you will memorise things well.(这里if就是如果不是虚拟语气)
If you have kept your mind clear,you would memorise things well.(这是虚拟语气,意思就是那人一定忘记了什么)