Which of the following factors favour the formation of oxyhaemoglobin? 

a.   high ${\mathrm{pO}}_2$

b.   low pH

c.   high temperature

d.   low ${\mathrm{pCO}}_2$

High ${\mathrm{pO}}_2$, low ${\mathrm{pCO}}_2$, low ${\mathrm{H}}^{+}$ concentration and low temperature favour the formation of oxyhaemoglobin.

Low ${\mathrm{pO}}_2$, high ${\mathrm{pCO}}_2$, high ${\mathrm{H}}^{+}$concentration (low pH) and high temperature favour the dissociation of oxyhaemoglobin.