He used to visit his parents _____, but he is too busy to call on them now. A every second weeks B every two weeks C every a few weeks D every two week
______ the aids from the outside, the positive attitude of the disaster-stricken people _____ the key role in the reconstruction of their destroyed towns and villages.
After several years of observation, the research group ______ the conclusion that language acquisition is faster when students ______ to the situation where it is spoken.