单选题 The following table includes a list of subjects at the  —— of scientific exploration.

单选题 For the time being, this computer system is still in its —— stages.

单选题 Due to his health problems, Richard has to give up hard  —— work on his farm.

单选题 Online stores are  —— and continually increasing their market share.

单选题 There is a growing ——to regard money more highly than quality of life.

单选题 My storybooks  ——most of the space of my two bookshelves in my bedroom.

单选题 Computer technology in all its phases from  —— to software has becomeless expensive.

单选题 Problem solving, like other mental activities such as creativity, is hard to  ——but generally easy to recognize.