According to mary ainsworth's "strange situation" research, when were children most willing to explore? when the stranger returned to the room after brief separation when the mother returned to the room after brief separation when their mother was present when their mother was out of the room

when their mother was present  

Explanation:

Through an experiment Mary ainsworth found that the behavior of one-year-olds is divergent, that is, depending on the type of bond they have established with their mother, will react to the different situations presented. Children, called “firmly bound”, that is, with secure attachment, explore, play with toys, approaching the stranger with care, only when the mother is present. However, when the mother leaves the room the child seems to lose the desire to explore the environment and play with toys.

a factory opens that mass-produces light bulbs.

explanation:

not sure if that's an answer to your questions but this is an example! : )