Final answer:
The subject of this question is English. The sentence provided is an example of a sentence using the past simple tense. Andy is tired because he worked all day.
Step-by-step explanation:
The subject of this question is English. The sentence provided is an example of a sentence using the past simple tense. In English grammar, the past simple tense is used to describe actions that were completed in the past. In this case, the sentence indicates that Andy worked all day, which is the reason why he is tired.
Learn more about Past Simple Tense