Travelers transiting through Singapore's Changi international airport for more than 5 hours can take a free tour of Singapore. In the daytime, travellers can take the Heritage Tour, which goes by the Colonial District, the famous Merlion fountain statue, Chinatown, and Little India. Travellers arriving at the airport in the evening can take the City Lights Tour which includes panoramic nighttime views from the Marina Bay Waterfront Promenade. The free tours will take you back to the airport in time to board your ongoing flight. Travel agents can supply full details.

top of the hour

Donald: Can I talk to you about the plans for the weekend?

Saori: I'm a bit busy at the moment; can I give you a call at the top of the hour?

Explanation: The phrase "top of the hour" means at the coming hour exactly. If someone tells you at 5:45 that they'll call you at the top of the hour, it means they will call you at 6:00 exactly. Think of the number 12 being at the top of the clock.

inhibit the growth

Patient: Can you completely remove the tumor?

Dr. Tariq: That won't be very easy. But we can give you treatment that will severely inhibit the tumor's growth.

Explanation: To "inhibit the growth" of a disease or a tumor means to strongly limit the growth of something. Some treatments will block, or almost block, the spread of a tumor.

opportunity cost

Dear Vanessa:
I don't think we should start the new marketing campaign. It wouldn't cost much money, but it will take many hours of our time. We could be doing something more profitable with that time. We have to think of the opportunity cost.

Explanation: The phrase "opportunity cost" means the money that you could lose because you're not doing something more profitable. If you close a store for one day to go fishing, you have the opportunity cost of losing your profits for one day.