A．Right-handed people are superior to left-handed people.B．Right-handedness is determined genetically, but left-handedness is learnt.C．About 18% of identical twins are left-handed.D．Scientists have not yet reached agreement on the causes of left-handedness.
A．Right-handed people are superior to left-handed people.
B．Right-handedness is determined genetically, but left-handedness is learnt.
C．About 18% of identical twins are left-handed.
D．Scientists have not yet reached agreement on the causes of left-handedness.