For some positive and distinct real numbers $x, y$ and $z$, if $\frac{1}{\sqrt{y}+\sqrt{z}}$ is the arithmetic mean of $\frac{1}{\sqrt{x}+\sqrt{z}}$ and $\frac{1}{\sqrt{x}+\sqrt{y}}$, then the relationship which will always hold true, is
- $y, x$ and $z$ are in arithmetic progression
- $\sqrt{x}, \sqrt{y}$ and $\sqrt{z}$ are in arithmetic progression
- $x, y$ and $z$ are in arithmetic progression
- $\sqrt{x}, \sqrt{z}$ and $\sqrt{y}$ are in arithmetic progression