Calculate the molar concentration of a weak monobasic acid if the acid dissociation constant $K_a = 1.8 \times 10^{-5}$ and the degree of dissociation $\alpha = 0.01$.

• A
  $1.8 \times 10^{-1} \text{ M}$
• B
  $1.8 \times 10^{-2} \text{ M}$
• C
  $5.55 \times 10^{-3} \text{ M}$
• D
  $5.55 \times 10^{-4} \text{ M}$