Solution:
Consider first (1) alone.
y<z<x. It gives no information about w.
If w > x, w will be maximum or else x will be maximum.
Since nothing definite can be said, (1) alone is not sufficient.
Next consider (2) alone.
If x is 25% of total of four investments, we cannot say which of w, x, y or z is maximum.
So (2) alone is not sufficient.
Next combine both statements together and check.
We have x = 25%*(w+x+y+z).
Or x = ¼*(w+x+y+z).
Or ¾*x = (w+y+z)/4.
Or x = (w+y+z)/3.
Let x > w.
So we have x > z, x > y, x > w.
Or 3x > (z+y+w)
Or x > (w+z+y)/3.
But since x = (w+y+z)/3 from (2), x > w is not possible.
Next let x = w.
So we get x = (x+y+z)/3.
Or 2x = y+z
Or x = (y+z)/2.
But we have been given that x > y and x > z.
This means 2x > (y+z).
Or x>(y+z)/2.
There is a contradiction. So x = w is not possible either.
So x < w is the only possibility.
Or w is the maximum investment.

The correct answer is (C)