Choose the best word that fits in the meaning of the sentences to make grammatical coherent.
Here, lack, missing and without mean same thing.
However, only 'without' correctly fits into the context and is gramatically correct.
The sentence would read as:
I. Governments in `these countries should create education systems since without good schools the bulk of people entering the world force will not have the skills they need.
II. We cannot process colour, details of rapid changes in our surroundings without the cone shaped cells packed around the centre of the retina.
Option D is correct option.