单选题 If you ____ in the contest, you could have won the first prize.

单选题 Would you mind giving us a demonstration ___ we can see how the machine works?

单选题 It's not uncommon for students to attend community college while ___ part-time.

单选题 It's a well-known fact ___ workplace design has an impact on employee happiness.

单选题 Real-time communication with friends in all parts of the world can be easily carried ___ with WeChat.

单选题 When we booked the hotel, little ____ what would happen once we arrived there.

单选题 The food we eat has the potential to either keep us healthy ___ contribute to weight gain or diseases.

单选题 The workers showed up on time, were very polite, and had the equipment ___ in a timely manner.