In this task, You are given an open-domain question that can be answered based on factual information. Your task is to provide \*short\* answer (in a few words only) for the given question. The short answer can be one or more entities or it can also be boolean \*yes\* or \*no\*.

who walked the tightrope between the twin towers
Philippe Petit

who has won the most trebles in scottish football
Celtic

to what class of enzymes does urease belong

metalloenzymes