1. overweight 
2. disagreement
3. unbelievable 

1. If your luggage is _overweight__, you'll have to pay an excess charge (weigh)
2. Jackson had another violent ___disagreement__ with the referee (agree)
3. The result was very strange! I fact it was _unbelievable___ (believe)
4. The advantage of living in the countryside is that the air is __unpolluted__. (pollute)
5. Samuel talked __endlessly___ about human cloning (end)
6. Her letter caused hi, some __uncomfortable___  (comfort)
p/s: đánh máy nhớ kiểm tra lỗi chính tả nha! :)))