Question: What is bowed string instrument whose famous person is Mstislav Rostropovich?
Choices: hurdy-gurdy
viola
harp
ukulele
electric violin
goblet drum
double bass
cello
fiddle
Appalachian dulcimer
SPARQL: SELECT DISTINCT ?e WHERE { ?e <pred:instance_of> ?c . ?c <pred:name> "bowed string instrument" . ?e <famous_people> ?e_1 . ?e_1 <pred:name> "Mstislav Rostropovich" .   }
Program:
function: Find
inputs: Mstislav Rostropovich
function: Relate
dependencies: 0
inputs: famous people
backward
function: FilterConcept
dependencies: 1
inputs: bowed string instrument
function: What
dependencies: 2
Answer: cello