Step 1: Recall the properties of a Geometric Progression (GP).
If \( a, b, c \) are in geometric progression, we know that:
\[
\frac{b}{a} = \frac{c}{b}
\]
or equivalently,
\[
b^2 = ac
\]
Step 2: Use the given relationship.
The given condition is \( a^x = b^y = c^z \). This implies the following:
\[
a^x = b^y = c^z = k (\text{for some constant } k)
\]
Taking logarithms of each equation:
\[
x \log a = y \log b = z \log c
\]
Step 3: Express the relationship.
From the properties of geometric progression, we know that \( \log b = \frac{1}{2} (\log a + \log c) \), so the relationships between \( x, y, z \) form an arithmetic progression.
Therefore, the correct answer is 1. Arithmetic Progression.