Which of the following best explains why Lignocaine has a higher fetal-to-maternal plasma ratio when compared with bupivacaine?
Lignocaine is  less protein bound than bupivacaine. Unbound form of drug thus easily gets transferred across placenta.
Bupivacaine has low molecular weight
Lignocaine has higher protein-binding
Bupivacaine has a lower dissociation constant (pKa)
Lignocaine is less protein bound