II. Choose the best answer to complete these following sentences. 
 
1. The children ate too much sweet ________ they get toothache easily. 
A. so       B.and      C.but      D.because 
 
2. Organically grown fruits and vegetables may not look as perfect, ________ it's good for your health. 
A.  so       B.and       C.however  D. therefor 
 
3. Thousand s of gallons of water were polluted ________some body spilled the motor oil and it swept into the ground. 
A.  because       B.so        C.and      D.however 
 
4. ________ we use less electricity, power plants will burn less fuel. 
A. If        B.So          C.Therefore      D.Because 
 
5. Old newspapers can be used to make newspapers, ________ you can collect them and bring them to the recycling center. 
A.  so        .B.because     C.and      D.therefore 
 
6. Don't use Styrofoam or aerosol spray ________ they both contain chlorofluorocarbons. 
A.  so      B.because      C.and  D. for 
 
7. Pesticides are chemicals poisons used by farmers to kill weeds and insect pests, ________ some pesticides are still in the food when it gets to the market. 
A.  so      B.because      C.and      D.however 
 
8. We use paper whenever we can, ________ the backs of envelopes or the clean backs of notebook sheets are great for scrap paper. 
A.  so      B. because      C.but     D.however 
 
9. He didn't go to school yesterday; ______.he had to ask his friends what they learned then. 
A. but        B.therefore     C.and        D.so 
 
10. The countryside is very peaceful ________ the air is so fresh. 
A.but       B.and      C.therefore         D.because