There is going to be a 25% chance of it being heterozygous unless both parents are heterozygous then if so you do happen to have to heterozygous parents it will be 100% heterozygous.
ANSWER: 50% or 2/4 EXPLANATION: E is a dominant trait and with a dominant E in the offspring it is not attached so half of the offspring would have non-attached earlobes and half would have attached earlobes.