Rational numbers are those values which can be expressed as a ratio of two integers. And it follows that irrational number are those which cannot be expressed as a ratio of two integers.
√5 is irrational as it produces a decimal sequence with no repeating pattern.
0.7 IS rational because it can be expressed as 7/10 (a ratio of two integers)
I suppose c) is meant to imply a sequence with no repeating patter, thus it would be irrational...
π has a decimal which has no repeating pattern and so it is irrational.
So the only rational number from your choices is 0.7 because it can be written as 7/10