Detailed Instructions: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Q: Passage: The 7.7 million day visitors and 5.5 million who made overnight stays on the Norfolk coast in 1999 are estimated to have spent £122 million, and secured the equivalent of 2,325 full-time jobs in that area. A 2005 survey at six North Norfolk coastal sites, including Blakeney, Cley and Morston found that 39 per cent of visitors gave birdwatching as the main purpose of their visit. The villages nearest to the Point, Blakeney and Cley, had the highest per capita spend per visitor of those surveyed, and Cley was one of the two sites with the highest proportion of pre-planned visits. The equivalent of 52 full-time jobs in the Cley and Blakeney area are estimated to result from the £2.45 million spent locally by the visiting public. In addition to birdwatching and boat trips to see the seals, sailing and walking are the other significant tourist activities in the area.The large number of visitors at coastal sites sometimes has negative effects. Wildlife may be disturbed, a frequent difficulty for species that breed in exposed areas such as ringed plovers and little terns, and also for wintering geese. During the breeding season, the main breeding areas for terns and seals are fenced off and signposted. Plants can be trampled, which is a particular problem in sensitive habitats such as sand dunes and vegetated shingle. A boardwalk made from recycled plastic crosses the large sand dunes near the end of the Point, which helps to reduce erosion. It was installed in 2009 at a cost of £35,000 to replace its much less durable wooden predecessor. Dogs are not allowed from April to mid-August because of the risk to ground-nesting birds, and must be on a lead or closely controlled at other times.The Norfolk Coast Partnership, a grouping of conservation and environmental bodies, divide the coast and its hinterland into three zones for tourism development purposes. Blakeney Point, along with Holme Dunes and Holkham dunes, is considered to be a sensitive habitat already suffering from visitor pressure, and therefore designated as a red-zone area with no development or parking improvements to be recommended. The rest of the reserve is placed in the orange zone, for locations with fragile habitats but less tourism pressure.
A:
What are the names of the three habitats that are designated as a red-zone area?