1 . Just an hour after completing her first aid course, Mamta was waiting at a bus stop when she heard a crash and saw a motorcyclist flying through the air—his helmet was going one way and his motorbike the ________. (用适当的词填空)

3 . Over the last two years, some supermarkets have started selling chicken or salad in packs designed with two halves containing separate portions (份). Then, when you use one section, ________ other stays fresh. (用适当的词填空)

4 . During a study of children, it was shown that if children are exposed to three or more years of musical training, they had better listening and speaking skills than ________ who had none. (用适当的词填空)