The correct answer is option 1: 53:52. This means that the ratio of students studying in Standard III of schools A and B together to those studying in Standard VI of schools C and D together is 53:52.

To understand this ratio, let`s break it down. The ratio states that for every 53 students studying in Standard III of schools A and B together, there are 52 students studying in Standard VI of schools C and D together.

This ratio gives us an idea of the relative number of students in these two grade levels across the different schools. It suggests that there is a slightly higher number of students in Standard III compared to Standard VI.

It`s important to note that this ratio is specific to the given schools and grade levels. The ratio may differ for other schools or different grade levels within the same schools.

Overall, option 1 represents the correct answer as it provides the respective ratio of students studying in Standard III of schools A and B together to those studying in Standard VI of schools C and D together.