1) People so often speak about ecology these day because this science is very important.
2) Ecology is an important science because it deals with world-wide problems for humanity and it is a science about our environment.
3) People first started speaking about ecology in the 20th century.
4) It uses the information of zoology, biology, chemistry, geography and some other sciences.
5) There are a lot of problems and the most important are different kinds of pollution ( air, water, land ), global warming, destruction of ozon layer and many other problems.
6) It has a great impact on every living thing, for example when we pollute water in rivers and lakes fish die and many animals have lack of food if they use fish as their food.
7) Human ecology studies the problems with nature which are connected with people.
8) My natural evironment isn't healthy. I live in a big city and it is very dirty because of cars and buses fumes. The air is bad and the soil is also polluted.
Насколько я поняла, здесь нужно поставить глагол в правильную форму, подходящую, собственно говоря предложению, например
I knew that she ... at school.
В троеточие стоит поместить слово work в том времени, которое подходит предложению, в данном случае, т. е workED