21. After several years of observation, the research group ______ the conclusion that language acquisition is faster when students ______ to the situation where it is spoken.
A. has come to; expose B. have arrived at; are exposed
C. has concluded; are exposed D. have reached; expose
22. Though _______ money, his parents managed to send him to university.
A. lacked B. lacking of C. lacking D. lacked in
