Regarding see and saw is this correct?
The boys saw the fire trucks across the street.
Regarding do and did is this correct?
They did their homework everyday.
Yes. Those verbs are correct.
However, "everyday" is an adjective. You need two words, "every day," in this sentence.
All of your alternative answers are correct depending on what time period you are talking about.
If the boys see the truck now, then "see".
If the boys saw the truck yesterday, then "saw".
If the boys do their homework every day this year, then "do".
If the boys did their homework every day last year, then "did".
Yes, both of the sentences are grammatically correct.
In the first sentence, "saw" is the past tense of "see." It indicates that the boys witnessed or observed the fire trucks across the street in the past.
In the second sentence, "did" is the past tense of "do." It is used to form the past simple tense, indicating that the action of doing homework occurred in the past. "Everyday" correctly explains that the action happened on a daily basis.
If you have further questions or need help with any other topic, feel free to ask!