Why do archaeologists know so little about how and why Stonehenge was constructed? O Archaeologists and historians cannot agree on a theory to explain Stonehenge. O Stonehenge was constructed thousands of years ago. © The builders of Stonehenge did not know how to write Druids used Stonehenge for secret religious ceremonies. 1 2​

good luck kid i beleve in you you can do it!

the verbal in this sentence is an infinitive. when you want to know the reason of an action, you simply ask the question "why? ". once you know the reason you can answer with "because".

many times we don´t use the word "because" but we can use another expression and that is an "infinitive of purpose". example:

-why did your brother bring a book?

-he brought a book to study.

in the answer above you can see an example of an infinitive sentence, just like in the example of your text. "he couldn´t run fast enough to beat his older sister". so, the answer is infinitive.