It does say that the court shall impose one of three possibilities. But then subsection 753(4.1) says that it has to be the indeterminate period unless the court is satisfied by the evidence that there's a reasonable expectation that a lesser measure would protect the public. That's putting the burden on the person before the court, as opposed to putting the burden on the prosecution to show that the indeterminate sentence is the appropriate response.
On November 14th, 2007. See this statement in context.