An irrational fraction is one that cannot be expressed as a simple ratio of integers.
Among the options provided:
a. A fraction with pi as the numerator or denominator - This is indeed an irrational fraction because \( \pi \) is an irrational number.
b. An improper fraction - An improper fraction is simply a fraction where the numerator is greater than or equal to the denominator. This type of fraction can be rational or irrational, depending on the numbers involved.
c. A fraction with 0 in the numerator - This fraction equals zero and is considered rational (not irrational) since zero is a rational number.
d. A fraction with a negative integer as the numerator - This fraction can also be rational, as any fraction where the numerator and denominator are integers (and the denominator is non-zero) is a rational number.
Thus, the correct answer is a - a fraction with \(\pi\) as the numerator or denominator is an irrational fraction.