Option 3 has error in it. Instead of "it is raining continuously" it should be "it has been raining continuously".
Thus the correct statement would have been "This pond is flooded with water because it has been raining continuously for the last three days".
As per me ....Option 3 but not Sure .... Weak in English ..
In this it is rainig continuously for the ..... in place of for the it should be since