Answer:
I think it would be a first option sorry if I'm wrong
<h2>Cambia el verbo en negrita y escríbelo en el presente perfecto. Change the verb in bold and write it in the present perfect.</h2><h3><em>Mariana, ¿nunca viste (2 palabras) las ruinas de Machu Picchu?</em></h3>
Answer : Mariana, ¿nunca has visto las ruinas de Machu Picchu?
Translation : Mariana, have you ever seen the Machu Picchu ruins?
Hope this helps!

Answer:
contestan
Explanation:
los estudiantes contestan las preguntas.
Answer:
radiometric dating
Explanation:
Some minerals in rocks and organic matter for example bones and shells can contain radioactive isotopes. Any of parent and daughter isotopes in a sample can be measured and used to determine their age. This is known as radiometric dating.