1. I ... understand what the patient was saying because he was speaking Chinese.
cannot / couldn`t / was able to
2. The child ... walk when he was 1 year old.
can / could / was able to
3. I ... eat fast food since I had gastritis/
cannot / couldn`t / haven`t been able to
4. When I graduate from the Medical university I ... to work as a doctor.
could/ will be able to / was able to
5. I arrived at the laboratory just as it was closing , so I ... get my blood test.