Compose a new way to ask the same question. The new question must be asking the exact same thing as the original question does. Without any other information, you should be able to tell that the original question and the new question are the same. Preserve bracketed phrases in your new question. You can change the rest of the question provided the above requirements are satisfied. The new question must have a natural, fluent formulation, as if it were composed by a native English speaker. You will be given three pieces of information to help you create better questions. Those are: "Answer": the answer to the question, e.g., "Honolulu". "Answer Type": the type of the answer, e.g., "Location". "Auxiliary Information" is a detailed description of some concepts mentioned in the question, if any.

original question: What class of drugs is [Vitamin D]?
answer: bisphosphonate, nicotinic acids, copper absorption inhibitor...
answer type: Drug class.
auxiliary information: Vitamin D refers to a group of fat-soluble secosteroids responsible for enhancing intestinal absorption of calcium, iron, magnesium, phosphate and zinc. In humans, the most important compounds in this group are vitamin D‚ÇÉ and vitamin D‚ÇÇ. Cholecalciferol and ergocalciferol can be ingested from the diet and from supplements. Very few foods contain vitamin D; synthesis of vitamin D in the skin is the major natural source of the vitamin. Dermal synthesis of vitamin D from cholesterol is dependent on sun exposure. Vitamin D from the diet or dermal synthesis from sunlight is biologically inactive; activation requires enzymatic conversion in the liver and kidney. Evidence indicates the synthesis of vitamin D from sun exposure is regulated by a negative feedback loop that prevents toxicity, but because of uncertainty about the cancer risk from sunlight, no recommendations are issued by the Institute of Medicine, for the amount of sun exposure required to meet vitamin D requirements. Accordingly, the Dietary Reference Intake for vitamin D assumes no synthesis occurs and all of a person's vitamin D is from food intake, although that will rarely occur in practice.
[Vitamin D] is listed in what class of drugs?

original question: How many medical treatments are being tested by [Physicians' Health Study]?
answer: 2
answer type: Medical Treatment.
auxiliary information: To assess the effect on cardiovascular mortality of alternate-day consumption of 325 milligrams of aspirin and, secondarily, the effect on cancer incidence of alternate-day consumption of 50 milligrams of beta-carotene.BACKGROUND: Thrombosis plays a major role in the late stages of coronary occlusion. Platelet aggregation is a large component in the formation of arterial thrombi. In pharmacologic studies, aspirin has been shown to inhibit platelet aggregation and, therefore, might be expected to prevent coronary occlusion. These effects are apparent in the dose range of l00-l000 mg/day, and may be most evident at l60 milligrams daily. Higher doses seem to be no more effective in either inhibition of platelet agreeability or prolonged bleeding time. Although an early case-control study by Jick and Miettinen showed a large benefit, most observational studies had shown a cardiovascular benefit of about 20 percent. Conclusive data could only result from a randomized trial with a large sample size. DESIGN NARRATIVE: Randomized, double-blind, fixed sample. Participants were randomized into one of four treatment groups: one 325 milligram aspirin tablet every other day, alternating with one 30 milligram capsule of beta-carotene; one aspirin every other day, alternating with one capsule of beta-carotene placebo; one aspirin placebo tablet every other day, alternating with one capsule of beta-carotene; and one aspirin placebo tablet every other day, alternating with one capsule of beta-carotene placebo. Major endpoints for the cardiovascular component of the study were cardiovascular mortality, total mortality, and coronary events.
How many different medical treatments are being tested by [Physicians' Health Study]?

original question: Which unit of energy density uses [International System of Units]?
answer: joule per cubic metre
answer type: Unit of Energy Density.
auxiliary information: The International System of Units is the modern form of the metric system and is the world's most widely used system of measurement, used in both commerce and science. It comprises a coherent system of units of measurement built on seven base units. It defines twenty-two named units, and includes many more unnamed coherent derived units. The system also establishes a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system was published in 1960 as the result of an initiative that started in 1948. It is based on the metre-kilogram-second system of units rather than any variant of the centimetre‚Äìgram‚Äìsecond system. SI is intended to be an evolving system, so prefixes and units are created and unit definitions are modified through international agreement as the technology of measurement progresses and the precision of measurements improves. The 25th General Conference on Weights and Measures in 2014, for example, discussed a proposal to change the definition of the kilogram.

[International System of Units] is used in what unit of energy density?