Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 26 to 30.

Urban development is having a direct impact on the weather in (26) ______ cities worldwide. It has been noticed that the difference in temperature is usually greater at night and the phenomenon occurs in both winter and summer. Experts agree that this is due to urban development, when open green spaces 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 (27) ______ 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, (28) ______ it is not uncommon to find plants growing on top of roofs or down the walls of large buildings. In Singapore, the government has (29) ______ 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 the creation of 18 "Supertrees" – metal constructions resembling very tall trees. Each one is a vertical freestanding garden and is (30) ______ 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.

Question 30: Each one is a vertical freestanding garden and is (30) ______ to exotic plants and ferns.