In an and condition, the most efficient technique is to first ask the question that "is least likely to be true".
If we look at the general rule or principle for an AND condition, it is to first make the inquiry that is less inclined to be valid. This would dispose of the same number of occasions of the second choice. By this the processing time will be fast. Thus the most proficient method for an AND condition is to first make the inquiry that is to the least extent liable to be valid. So, the right choice is c.