instruction:
In this task, you're given a context, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both context and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the context or linked information.
question:
Context: the group originally included lead vocalist Keith Relf Link Information: The Yardbirds are an English blues rock band from London. Formed in May 1963, the group originally included lead vocalist Keith Relf Answer: Robert Plant
answer:
Which person was the lead singer of the Yardbirds the longest?

question:
Context: During the process of electing Leopoldo Calvo-Sotelo as Spain's new president in February 1981 Link Information: Leopoldo Ramon Pedro Calvo-Sotelo y Bustelo, 1st Marquess of Ria de Ribadeo (; 14 April 1926 3 May 2008) Answer: 55
answer:
How old was Leopoldo Calvo-Sotelo when elected president?

question:
Context: He was drafted by the Oakland Raiders in 1999 Link Information: Under Gruden, the Raiders posted consecutive 88 seasons in 1998 and 1999 Answer: Jon Gruden
answer:
Who was the head coach of the team that drafted Armour, at the time he was drafted in 1999?