Grammar ( 有選擇)

lamleo1993 got all the answers right.
1. be playing (future continuous tense because "this time next week")
2. be working (after "can't", it should be followed by an infinitive - "be" in this case)
3. to be working (after "seemed", normally it is followed by to be)
4. to sit (need is a "to-infinitive", should be followed by "to")
5. giving (present continuous tense)

1.be playing(verb is needed)
2.be working(verb is needed, "can't" isn't a verb)
3.working(participle)
4.to sit(to-infin)
5.giving(p.c.)

1.be playing
2.working
3.to be working
4.to sit
5.giving

1. This time next week I'll be playing on the beach.
2. Why is he so late? He can't still working.
3. I noticed that you seemed to be working a lot.
4.I need to sit down because my legs hurt.
5. That loud music is giving me a headache!

1. be playing
2. working
3. working
4. to sit
5. giving