Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate to correct word or phrase that best fits each of the numbered blanks from 27 to 31.

Urban development is having a direct impact on the weather in many cities worldwide. It has been noticed that the difference (27)________ temperature is usually greater at night and the phenomenon occur in both winter and summer. Experts agree that this is due to urban development, when open green space are replaced with asphalt roads and tall brick or concrete buildings. These materials retain heat generated by the Sun and release it through the night. In Atlanta, in the US, this has even led to thunderstorms (28)________ occur in the morning rather than, as is more common, in the afternoon. Large cities around the world are adopting strategies to combat this issue (29)_______ it is not uncommon to find plants growing on top of roofs or down walls of large buildings. In Singapore, the government has (30)________ to transform it into a "city within a garden" and, in 2006, they held an international competition calling for entries to develop a master plan to help bring this about. One outcome was thecreation of 18 "Supertrees"-metal constructions resembling very tall trees. Each one is a vertical freestanding garden and is (31)________ to exotic plants and ferns. They also contain solar panels used to light the trees at night and also containers to collect rainwater, making them truly self-sufficient.