Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Ex Input:
The Gruffalo is a children's book by writer and playwright Julia Donaldson, illustrated by Axel Scheffler, that tells the story of a mouse, the protagonist of the book, taking a walk in a European forest.

Ex Output:
What person illustrated The Gruffalo?


Ex Input:
Restless legs syndrome/Willis-Ekbom disease (RLS/WED) is commonly seen in patients with end-stage renal disease (ESRD), but this condition has not been properly recognized. The prevalence of RLS/WED in ESRD shows the ethnic variation (7%-68%), with the similar tendency of primary RLS/WED. Although RLS/WED in ESRD is defined in secondary RLS/WED, the factors of ESRD that are involved in the genesis of RLS/WED remain unknown. Even after renal transplantation, RLS/WED symptoms do not completely disappear, and genetic predisposition to RLS/WED may play an important role in causing RLS/WED. Long-term intervention for RLS/WED and ESRD will be necessary.

Ex Output:
Willis-Ekbom disease is also known as?


Ex Input:
The Minnesota River is a tributary of the Mississippi River, approximately 332 miles (534 km) long, in the U.S. state of Minnesota.

Ex Output:

Of what river is Minnesota River a tributary?