41) the methods for studying the earth........been being researched
A. have B. has C. having D. to have
42) to love and to be loved the.......the greatest happines on earth
A. is B. are C. be D. were
43) the boy and the girl.........their parents dearly
A. love B. loves C. loving D. to love
44) no teacher and no student..........present at the classroom on sundays
A. is B. are C. be D. were
45) what.......the purpose of learning foreign languages
A. is B. are C. be D. were
