I. Governments in `these countries should create education systems since ......... good schools the bulk of people entering the work force will not have the skills they need.
II. We cannot process colour, details of rapid changes in our surroundings ......... the cone shaped cells packed around the centre of the retina.

Here, lack, missing and without mean the same thing.
However, only 'without' correctly fits into the context and is grammatically 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 workforce 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.