Suppose we are told that the acceleration of a particle moving in a circle of radius r withuniform speed v is proportional to some power of r, say r^n , and some power of v, say v^m , determine the powers of r and v

I would look at the units.

r . . . meters
v . . . meters/second
and
acceleration . . . meters/second^2 .

1). The only way to get sec^2 on the bottom is to use v^2.
That gives you (meters^2)/(sec^2).

2). If you divide that by meters,
you have (meters)/(sec^2), and THERE'S your acceleration !

So we know that (v^2)/(r) is acceleration.

In terms of the way the question is written:

v^m = v^2. m = 2 .

r^n = 1/r. r = -1 .

Ithink it is letter b, i may be wrong but i think that is the answer

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.