The graph illustrates how different partial pressures of carbon dioxide ($\text{CO}_2$) alter the oxygen dissociation curve for haemoglobin. What change occurs in the percentage oxygen saturation of haemoglobin at a partial pressure of oxygen of $6\,\text{kPa}$ when the partial pressure of carbon dioxide rises from $1.0\,\text{kPa}$ to $1.5\,\text{kPa}$?
- A$-26\%$
- B$-20\%$
- C$20\%$
- D$46\%$