单选题 The quality of products may ____ among different brands.

单选题 Thanks to the discount, the shoes became____ for me.

单选题 I____ a wallet on the sidewalk and immediately handed it in to the police.

单选题 He brought____to his family by dropping out of school.

单选题 The team will____their research findings at the conference.

单选题 The company has made____ investments in research and development this year.

单选题 ____is essential for science fiction writers.

单选题 The company is involved in an____ research on new technologies.