Question

The water cover 71% of the earth very little can be used by humans give reasons

Answer 1

because the 71% of water which covers the earth is salty water or the oceans water which are not good for drinking and using purposes the water which is fit for drinking is 0.01% availability of that water hence the 71% of water which covers the earth is not usable for human

Answer 2

71% water is present in oceans and we can not use it because it is very salty.. and we have do too much process to filter it which cost so much..

We have only 2.5% fresh water which is usable.. which present in glaciers and underground.. which is directly accessible by us..

That's why we can't use that 71% available water..