Why might a factory be interested in hiring children?

For one thing, children have more energy and tend to able to stay awake longer than adults. They also can work all the way up until they are adults, which means they will not retire till many years later. The younger the children the less they would most likely need money. The factory owners would not have to pay them large portions of money as they would for adults.

(d) it was complex and capable of highly organized efforts.