The input hypothesis involves four main issues. What are they?

The input hypothesis involves four main issues. What are they?
【正确答案】：(1) THE HYPOTHESIS RELATES TO ACQUISITION,NOT TO LEARNING;(2)PEOPLE ACQUIRE LANGUAGE BEST BY UNDERSTANDING INPUT THAT IS SLIGHTLY BEYOND THEIR CURRENT LEVEL OF COMPETENCE;(3) THE ABILITY TO SPEAK FLUENTLY CANNOT BE TAUGHT DIRECTLY;(4) IF THERE IS SUFFICIENT QUANTITY OF COMPREHENSIBLE INPUT,I+1 WILL USUALLY BE PROVIDED AUTOMATICALLY.