The sentence José Miguel está cansado porque trabaja mucho means that José Miguel is tired because he works hard, so he's a hard worker is a person who is diligent in carrying out tasks or duties. So the reason why this man is tired is because he's a hard worker. In other words, José Miguel works a lot.
Un huracán means a hurricane and is a violent storm with extremely strong winds and heavy rain. Thus, los viajeros están preocupados porque va a pasar un huracán means that travelers are worried that a hurricane will happen. Perhaps they are worried because they know that hurricanes destroy everything they find.
It is snowing outside and Maribel and Claudia are sad because they won't be able to go out. In this sentence, we have the word están that comes from the verb estar and is the conjugation of this verb for the third person plural in the simple present. Here we use this verb as emotions, expressing what a Maribel and Claudia are feeling at a certain moment
If the answer of some students is incorrect, then they are wrong. So in this sentence, the students are wrong. Here we also use the verb estar conjugated as están because this conjugation stands for the third person plural in the simple present, that is, we can replace los estudiantes by the subject pronoun that matches the third person plural, which is ellos. Finally:
Los estudiantes están equivocados porque su respuesta es incorrecta
Laura is in love with her boy friend because he's friendly, intelligent and handsome. According to this sentence she loves his mind and body. In this sentence we use the verb estar conjugated as está that matches the third person singular in the simple present. Here we use the verb estar as relationship, describing a romantic relationship between two people.
