根据句意用括号中所给单词的适当形式填空。 1. I'd like a pair of _____, please (shoe). 2. They talked on and on very _____ (happy). 3. The _____ are building a tall building. (work) 4. This bag isn't Lucy's , It's _____ sister's. (she) 5. The first lesson is the _____ of all. (easy).