1.what is the latitude of the direct(vertical) rays of the sun?

2. a). what is the latitude of the tangent rays in the northern hemisphere?

b.) what is the latitude of the tangent rays in the southern hemisphere?

3. why is june 21st associated with the southern hemisphere winter?

As explained below.

Explanation:

The sun rays reach the earth's surface at an angle of 90 degrees at the equator which is direct and is short as compared to the poles it's long and about 66.5 degrees to the south and north. In the tropics its falls as 23.5 degrees in the northern and southern hemisphere.  The sun rays that form a tangent to the northern hemisphere are at 0, 23.5, 66.5 degrees i.e tropics, temperate and poles. And same is for the southern hemisphere. On June 21 the southern hemisphere has winter seasons as the amount of insolation that reaches the southern side is less due to the tilt of the sun.

Don’t use up to much of them it leads to pollution

It is nonrenuable which means that once you have used it, it's gone forever.