pH and pK Practice Test

For the weak acid HF in water, $K_a=1.0\times10^{-4}$ at $25^\circ\text{C}$. Which relationship between $K_a$ and $pK_a$ for HF is correct?

A weak acid HA has $K_a=1.0\times10^{-5}$ at $25^\circ\text{C}$. Which value is closest to $pK_a$ for HA?