Mankind has never experienced changes in life and work on such a scale.
The task of the world community is to improve the ecological situation in the world.
In six years we shall become engineers.
Нужно задать к каждому альтернативный,специальный,разделительный и общий вопрос.

Has ever mankind experienced changes in life and work on such a scale?
Mankind has never experienced changes in life and work on such a scale, has it?
What has mankind ever experienced?
Has mankind ever experienced changes or stability in life and work?

Is the task of world community to improve the ecological situation in the world?
The task of world community to improve the ecological situation in the world, isn' t it?
What is the task of world community?
Is the task of world community to improve the ecological or economic situation in the world?
Shall we become engineers in six years?
In six years we shall become engineers, shan't we?
What shall we become in six years?
Shall we become engenders or teachers in six years?