Choose the best answer to complete these following sentences

Ex 4- Choose the best answer to complete these following sentences.
1. _____ she was very tired, she helped her brother with his homework.
A. Because        B. whether              C. Although             D. so
2. It’s raining hard, _____ we can’t go to the beach.
A. or                  B. but                     C. so                     D. though
3. Nam was absent from class yesterday ____ he felt sick.
A. so                B. because              C. although             D. but
4. Tom has a computer, _____ he doesn’t use it.
A. or                B. as                       C. because               D. but