To complete the passage about ancient aviators, we need to use the correct forms of the words provided in the box: be, disagree, do, include, know, look, see, seem, and understand. The context of each sentence will guide us in choosing the appropriate word and form.
Everyone knows that humans have been flying for only a few hundred years. This sentence needs the simple present form of "know" because it states a general belief or fact.
But is it possible that ancient civilizations also had the ability and technology to fly? Here, we need the present simple form of "be" to pose a question about possibility.
On the ground, they just look like straight lines. The verb "look" fits here to describe the appearance of the lines from the ground.
But when you see them from the air, you understand exactly what they are. "See" is used in the context of observing from a different perspective, and "understand" is appropriate for realizing or comprehending the nature of the lines.
The pictures include animals, birds, and symbols. "Include" is the correct choice here to indicate that animals, birds, and symbols are part of the pictures.
One bizarre theory, which most mainstream scientists disagree with, is that the people who made the lines thousands and thousands of years ago flew above the lines in balloons. "Disagree" is used here because it conveys that most scientists do not support this theory.
It seems incredible, but a few people do believe it's possible. "Seems" is used to express how the theory appears to people, and "do" is used for emphasis in the present simple tense to show that despite the incredibility, some people indeed believe in the theory.
So, the completed passage reads as follows:
Everyone knows that humans have been flying for only a few hundred years. But is it possible that ancient civilizations also had the ability and technology to fly? In the Nazcan Desert in southern Peru, there are hundreds of lines which an ancient culture drew in the dust. On the ground, they just look like straight lines. But when you see them from the air, you understand exactly what they are. They are incredible and enormous pictures. The pictures include animals, birds, and symbols. One bizarre theory, which most mainstream scientists disagree with, is that the people who made the lines thousands and thousands of years ago flew above the lines in balloons. It seems incredible, but a few people do believe it’s possible.
