Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.

[EX Q]: Context: When the Federal German Navy was established in 1956, Dochet and Flint were acquired and classified as Type 139 patrol trawlers.
Question: What year was Type 139 patrol trawler made?
[EX A]: 1956

[EX Q]: Context: With transform plate boundaries, the two slabs of lithosphere are sliding past each other in opposite directions. The boundary between the two plates is a transform fault. Transform faults on continents separate two massive plates of lithosphere. As they slide past each other, they may have massive earthquakes. The San Andreas Fault in California is perhaps the worlds most famous transform fault. Land on the west side is moving northward relative to land on the east side. This means that Los Angeles is moving northward relative to Palm Springs. The San Andreas Fault is famous because it is the site of many earthquakes, large and small. (Figure At the San Andreas Fault in California, the Pacific Plate is sliding northeast relative to the North American plate, which is moving southwest. At the northern end of the picture, the transform boundary turns into a subduction zone. Transform plate boundaries are also found in the oceans. They divide mid-ocean ridges into segments. In the diagram of western North America, the mid-ocean ridge up at the top, labeled the Juan de Fuca Ridge, is broken apart by a transform fault in the oceans. A careful look will show that different plates are found on each side of the ridge: the Juan de Fuca plate on the east side and the Pacific Plate on the west side.
Question: over millions of years, which direction would you find los angeles in relation to where it is now?
[EX A]: north

[EX Q]: Context: The first step in the management of restless legs syndrome (RLS) is to identify, and if possible to treat any condition which might cause or worsen RLS, such as iron deficiency or some drug treatments. The patients suffering from RLS should be prompted to keep a healthy sleep schedule. Drug treatment should be restricted to patients with a clear clinical diagnosis, decided on an individual basis, when the clinical impact is serious. Four drug classes are central to the treatment of RLS: dopaminergic agents, some antiepileptics, opioids, and benzodiazepines. Dopaminergic agonists are the treatment of choice, especially when daily treatment is indicated, or if the symptoms are severe. Two dopaminergic agonists are licensed in France for the treatment of RLS: ropinirole (Adartrel) and pramipexole (Sifrol). After initiation of treatment, the patients should benefit from a regular follow-up in order to evaluate the efficacy of treatment and to identify possible side-effects. Special care should be given to the detection of augmentation, a phenomenon characterized by a paradoxical worsening of the symptoms with treatment. Some particular conditions, such as RLS comorbid with renal insufficiency, during pregnancy, and in the child are discussed.
Question: Which deficiency is the cause of restless leg syndrome?
[EX A]:
iron