Complete the sentences. Use the present simple and present continuous in each pair.
1. a) He ... (not wear) a school uniform today.
    b) He always ... (wear) sports clothes.
2. a) Our teacher ... (work) now.
    b) She ... (not work) at the weekends.
3. a) I ... (not use) a computer at the moment.
    b) We sometimes ... (use) computer.
4. a) We ... (study) English at the moment.
    b) We ... (not study) English every day.