How do the underlined phrases support the author’s purpose? They show that many friendly people live in the area.
They show that the migrants are not needed in these fields.
They show that the worst part of the train ride may be over.
They show how much time has passed since the ride began.

This question is missing the excerpt with the underlined sentences. I was able to find it online:

Read the excerpt from "Enrique's Journey":

The train passes into northern Chiapas. Enrique sees men with h.o.es tending their corn and women inside their kitchens patting tortillas into shape. Cowboys ride past and smile. Fieldworkers have their machetes and cheer the migrants on: "Qué bueno!" Mountains draw closer. Plantain fields soften into cow pastures. Enrique's train slows to a crawl. Monarch butterflies flutter alongside, overtaking his car.

NOTE: I typed h.o.es like this so that will not interpret it as a bad word.

The underlined phrases support the author's purpose because:

C. They show that the worst part of the train ride may be over.

Explanation:

American journalist Sonia Nazario (born 1960) won the Pulitzer Prize for "Enrique's Journey", which tells the story of the 17-year-old boy from Honduras and his journey to be reunited with his mother.

In the particular passage we are analyzing here, the author is describing a transition. The landscape changes once Enrique reaches Chiapas, a region in Mexico. The boy can now see several people, their homes, cow pastures, and mountains. His train also slows down. The author gives such details to show that the worst part of the train ride may be over. This is a sign that Enrique has already conquered a great deal of his journey.

the present continuous is a verb tense which is mainly used to indicates that an action is in progress at the moment of speaking.  

it is formed using: person + verb to be (am/is/are) +verb + - ing form  

example: i am studying at this moment .

in addition, the present continuous is also used in order to express things that will or will not happen in the near future.

example: i am having dinner with some friends tonight.

the speaker sometimes   uses it   to express that an action is repeated and it causes irritation on the part of the speaker

example: my sister is constantly complaining about everything.

heylo !

explanation: