What Environmental Cue Makes Ducklings Follow Their Mothers or 'Imprints

Multiple Choice

What environmental cue makes ducklings follow their mothers or 'imprints' her image on their minds?

A) they hear them calling when still in the egg and recognize the call once hatched
B) their moms are usually the first moving thing they see
C) they understand how hard it is to sit on eggs all day
D) hunger
E) scent