What is child’s third biggest export

Can someone answer this pls ill give brainliest both ser and estar mean ‘to be’. in what situations do we use estar? estar, venir, and ir are considered irregular verbs. what makes a verb “irregular”?

Pongo la carta dentro de uno de estos

Can somebody me out with this spanish question? completa la oración con la voz pasiva con se. used cars for sale. carros usados. (the answer is not usa los or venta de)