In your opininon, what is the biggest problem in the world?

Lately, science, and technology have developed a lot by humans, but we wasted a lot of bad things too, thay is why we cause the problem. In my opinion, the biggest problem is global warming because the big amount of water is increasing, and it will keep increasing.
It is very simple to know who, and what cause the global warming , it is us, and cars, factoris...etc. The gas that comes out from the cars and the factoreis is very bad, also many people have the cars, it makes even worse, it makes earth really warm. the reason why I said it is us who cause problem is we made the cars, threw the garbages on the ground, and we use cars factories...etc.
People should be awarre of global warming. What is going to happen is the ice that has been frozen for a long time will melt because of high temperature. So if we keep making the earth warm, one day, we are going to have to live under the water because water is going to be covering the lands, which means that we are not going to be able to live on the land, land is disapppeared by water.
The best wat to fix this prolbem is that we go to use the cars lessly, we go to develope such things as electric car, but one big things is even though we made this, if we don't use it there is no point, so not only me, everyone has to cooperate to solve the problem.
It is going to be very awful if we can't live on the land, there are going to be more problems that we have not, but if we start, try really hard to solve, we can do it.