It's easy _______a sandwich. 

In societies where social roles are determined, boys usually copy the behavior of their fathers, and girls usually also copy _____ of their mothers.

Within industries，companies are always trying to develop products that are one step better than _____ of other companies．

---What can I do for you?---I am looking for a birthday gift for my sister, _______at a proper price but fashionable.

I always think that while we are in the world,we should try         .