4. all of us should pay attention to quality_______ quantity a. instead of b. in need of c. because of d. instead 5. the lake in my hometown is so seriously_______ that all the living things died out gradually. a. polluted b. polluting c. pollute d. to pollute 6. ______ i admit that the problems are difficult, i don’t agree that they cannot be solved. a. when b. as c. because d. while 7. i’ve enjoyed______ to talk with you.